Volume Vi, No. 4; Volume Vii, No. 6; Volume Viii, No. 2; Plague Among

the Ground Squirrels of California, W. B. Wherry, Journal Infectious Diseases, Volume V, No. 5; California Mammals, Frank Stephens.

RODENT EXTERMINATION.

By Passed Asst. Surg. WILLIAM COLBY RUCKER,

United States Public Health and Marine-Hospital Service.

It should be remembered that rodents are extremely wily creatures and that any campaign against them is a contest between the wit of man on the one hand and acute animal instinct on the other. The rat, by his constant association with man, has become extremely wary, and is frightened by anything in the least out of the ordinary. They will eat the bread on which poison is spread so carefully that they will leave behind the poison and take practically all the bread; they will open traps by pressing down the pan, and they have been known to repeat this operation several times within an hour, entering the trap, eating the bait, and then liberating themselves. At other times they will enter the trap and stand on the pan with their hind legs, eat the cheese, then carefully turn around and back out. This, of course, is not possible with snap traps, but they have been known to spring them by causing pieces of wood to fall upon them, after which the bait would be eaten. Rats are found wherever food exists in abundance or where they can find suitable breeding and nesting places.

Rodent extermination is a problem, with difficulties arising from the animal’s highly developed regard for self-preservation. In main, the rat requires two conditions for life. He needs plentiful food and places suitable for nesting and breeding. Eliminate either of these elements and you drive away your rats. Yet the problem remains far more difficult than shown in the simple terms of the above equation. The fabulous speed at which rats multiply will baffle all but the most determined and efficient efforts to exterminate them. Under normal conditions each female bears 3 litters a year and each litter produces 10 young. Under conditions ideally favorable, it has been computed that 1 pair of rats will in five years, providing all can live so long, increase to 940,369,969,152. Such a result is, of course, impossible in nature, for it means that every rat born of the original pair survive five years; that every litter of 10 contains 5 males and 5 females; and that the ideally favorable conditions persist. On the other hand, rodent existence is an unending struggle in which an enormous percentage succumbs; the ratio of half males and half females does not hold; and ordinary conditions of life are hardly even favorable. Nevertheless, the above proves emphatically that no rat eradication can be effective unless the breeding is curtailed. Any campaign against rodents must aim (a) to slaughter the greatest possible number of those already living and (b) to prevent the possibility of further breeding.

The existing rats are best attacked by trapping, by poisoning, and by their natural enemies. Traps and poisons alone have been found insufficient to keep pace with the rat’s speed of multiplication. The surest of the rat’s enemies are his natural ones, and once they have been loosed upon him his chance of escape is reduced. The cat, dog, skunk, and other rodent foes, given a fair chance, quickly drive out rats. But these animals do not eradicate the pest. The rats will probably migrate to some other shelter, returning when their natural enemies have quieted down. Absolute extermination is reached only when conditions make the continuation of species impossible for the rat.

The size and frequency of rodent litters decreases proportionately with every cutting off of food supplies. Separate the rat from his pabulum and he will not breed so freely nor so often as when he is well fed. Destroy rat habitations and make it impossible for them to find new nesting places, and breeding will virtually cease, since the unsheltered progeny can no longer survive, and since the starving parent rats are driven to cannibalism in the struggle for existence.

Campaigns against rodents must cover five directions: (1) Trapping, (2) poisoning, (3) exposing them to natural enemies, (4) cutting off food supply, and (5) destroying existing nests at the same time that the making of new ones is prevented.

Parenthetically, it may be noted that while these principles apply equally to the extermination of rats in cities and in country districts, their application must vary according to the place.

TRAPPING.

The kind of traps to be used varies with the rodent to be captured and the locality which it infests.

CAGE TRAPS.

The large 19-inch French cage trap gives good results where rats are plentiful. It should be made of stiff, heavy wire and well reenforced, as a large, strong rat will force his head between the wires in a weak trap and thus escape. Before setting, the lever on the trap should be tested to see that it works properly. The trap should be placed on a hard surface, with the rear end a little higher than the entrance, so that the trap will close promptly. When setting the trap in the open it should be fastened to a board on which about an inch of soft dirt has been spread. Place the trap where the rat usually goes for food or in a runway and disturb the surroundings as little as possible. It is sometimes well to place the trap near where there is dripping water, as the rats come there to drink. If the trap is set in hay or straw or wood it should be covered (with the exception of the entrance) with this material. When this is not possible it should be covered with a piece of sacking or placed in a dark corner or beneath the floors. When setting the traps in the sewer a dry place should be chosen.

The rat is more or less of an epicure, therefore the bait should be changed at frequent intervals. Also he should be given food which he is not in the habit of getting. For example: In a meat market vegetables are the best bait, while in a location where vegetables are plentiful fresh liver and fish heads, or a little grain, are best. The following may be suggested as good bait to be used: Fish, fish heads, raw meat, cheese, smoked fish, fresh liver, cooked corn beef, fried bacon, pine nuts, apples, carrots, and corn. When trapping in chicken yards a small chick or duckling is remarkably good. When a large number of rats are caught in one trap, search for the female and leave her alive in the trap, as she may call in the young or the males. The bait should be fastened to the inner side of the top of the trap with a piece of fine wire so that the first rat in can not force the bait underneath the pan and thus prevent the entrance of other rats. A few grains of barley should be scattered near the entrance of the trap and a small piece of cheese or meat fastened to the pan with a piece of wire. It is often well to touch the pan with a feather which has been dipped in oil of anise or oil of rhodium. Before leaving the trap it should be smoked with a piece of burning newspaper to kill the smell of the human hands or the rats which have been in it. Do not handle the trap after burning it out. When trapping in a neighborhood where rats are known to exist the traps should not be moved for three or four days unless they have rats in them, as it is well for the rats to become accustomed to seeing them and thus careless about entering. It is not wise to kill rats where they are caught, as the squealing may frighten the other rats away.

SNAP TRAPS.

Snap or spring traps are best for use in houses and stores, with the exception of fish and meat markets. Snap traps are best for use in runways, beams, and shelves. It is sometimes well to disguise the trap by covering its floor with a little sawdust or dirt. They should be first tested to see that they work properly and that the staples are secure. New traps should be smoked or stained to render them an inconspicuous color.

The bait should consist of some firm material, such as fried bacon or tough meat, and should be tied on so that the rat will be obliged to pull on it and thus spring the trap. The trap should be placed in a corner or close to the wall on a flat, hard surface, so that the rat can not spring it with his tail or by walking on it.

BARREL TRAPS.

In warehouses and granaries large numbers of rats may frequently be trapped by using a barrel or garbage can having a metal top which is carefully balanced. Large pieces of strong cheese are placed in the middle of the cover and a plank laid from the floor to the edge of the barrel. The rat runs up the plank onto the smooth metallic lid which tips and the rat is precipitated into the barrel.

In cities trapping is one of the most effective of the three methods to slaughter rodents. The rat highways are easily discovered and in them traps capture great numbers of the unwary. In the country one can not so readily determine the rat highway. This difficulty diminishes the effectiveness of trapping. To make up for what is thus lost shooting has been resorted to with good results. In Honolulu, where a vigorous campaign against rodents is being waged, a very large proportion of the captured rats (Mus rattus and M. alexandrinus) have been shot from trees. In Contra Costa County, Cal., where ground squirrels are being exterminated, it has been found that rodents possess an instinctive suspicion of traps and that during the summer months shooting is not only the most practical but also about the only effective means of attacking them. Shotguns are the weapons to use. A rifle requires the hunter to be a better shot than is ordinarily obtainable for such work, and, furthermore, the danger from its longer range and from ricocheting bullets menaces cattle and farm hands who may be working in the vicinity. As to the shot and the powder charge for shells hunters differ. It is a different problem for every shotgun, depending upon the gun’s caliber and choke. The principle is to put the greatest number of the largest shot the gun will carry into the rodent body. Thus in 10 and 12 gauge guns shoot No. 8 shot and in 16-gauge guns shoot No. 9 shot, but this varies with each individual gun. The use of soft lead or chilled shot seems a matter for personal preference. The charge must be as much as the gun will carry. In the country smokeless powder becomes a necessity during summer months since black powder is liable to ignite the dry grass and stubble.

POISONING.

PLASTER FLOUR.

Plaster flour is prepared by mixing one part dry plaster of Paris with two parts flour or meal. When this is taken in sufficient quantity by the rodent it produces death by the formation of enteroliths, death occurring in from four to eight days. This is a poison of uncertain value and is recommended chiefly on account of its cheapness and small danger to children and domestic animals. It can not be used in wet weather, and judging from the small number of rats found dead with plaster casts in the alimentary canal it is not believed to be very efficacious.

PHOSPHORUS PASTE.

Phosphorus paste is prepared by mixing crude phosphorus in the proportion of one-half to 10 per cent in a suitable base. The latter may consist of cheese, sugar, and oil of anise mixed together and heated to the consistency of sirup, the phosphorus being added after the fire has been withdrawn and the mixture begun to cool. Other bases are cheese, corn meal, and oil of rhodium; cheese, ground fish, or meat and oil of valerian, glucose, and a small quantity of flour. Glucose makes an exceptionally good base, as when properly mixed the poison thus prepared is noninflammable even when heated. The liability to spontaneous combustion of phosphorus mixtures eliminates their use in hay, grain, or other warehouses or places where there is danger of fire or the invalidation of insurance. It should not be forgotten that phosphorus deteriorates very rapidly, especially when it is exposed to the sun.

ARSENIC PASTE.

This consists of arsenious acid combined with a base of cheese, meal, or macerated fish. It may be placed on raisins or prunes and is to be recommended on account of its stability, the ease with which it is handled, and the absence of danger from fire. It should, however, be distributed with great care, every precaution being used to place it where it is inaccessible to children and domestic animals.

BARIUM CARBONATE.

This has not proven an effective poison owing to the fact that it is easily decomposed by the vegetable acids, especially lactic and oleic acid found in cheese and oil. The poisonous effect is not greatly altered by this change. A disagreeable metallic taste is produced and the rats will not take it.

STRYCHNINE.

Strychnine is prepared as a poison by soaking wheat over night in water and subsequently pouring off the excess fluid and placing the wheat in a caldron containing hot glucose and strychnia sulphate, the latter in the proportion of one-tenth of 1 per cent. After carefully stirring so that each grain is thoroughly coated it is dried in shallow iron pans over a slow fire with constant agitation of the grain, or by exposure on sheets or canvas to the rays of the sun. This mixture may be made much more efficient by the addition of cyanide of potassium in the proportion one-half of 1 per cent. Poisoned grain has not been found efficient in the destruction of rats, as its bitter taste causes them to eat little or none of it. It is, however, particularly efficient in poisoning squirrels, as it is taken readily by them. The chief objections to its use are its cost, difficulties of preparation, and liability to its being taken by chickens.

CARBON BISULPHIDE.

Carbon bisulphide is not a poison so much as an asphyxiant. As the name indicates, it is a two-to-one mixture of sulphur and carbon. The resulting liquid preparation should be kept in air-tight cans, since it evaporates quickly. The principle of its efficacy against rodents is that the fumes are heavier than air and, sinking into a rat or squirrel hole, drive out the necessary oxygen. To use bisulphide saturate a small pad of some absorbent cotton, jute, wool, or flannel material with the liquid, thrust this into the rodents’ burrow, and carefully stop all apertures through which the fumes might escape. Animal life of every sort in that burrow is quickly asphyxiated. In buildings the use of carbon bisulphide is greatly hampered by the difficulty to confine the gas by stopping all cracks and other openings. Also the odors of decomposition in animals so killed stand against its use anywhere but in the country.

Against rats and squirrels in country places carbon bisulphide has proved one of the best of all weapons. Where it kills, it kills whole families at a time, not one by one, as must ever be the case with other poisons and with traps or shotguns. Not only does it kill the rodent but it also destroys the rodent’s fleas and vermin, which is most important. A dead infected rat is still a menace, since its fleas may inoculate other rats and human beings with the infection. Destroy the fleas and that greatest danger is removed. The recent campaigns against rodents in the United States have been waged because rats and squirrels were infected with bubonic plague; hence the added value of carbon bisulphide. Unfortunately, though this asphyxiant proved so effective in the work against squirrels in Contra Costa County, Cal., it proved to be well-nigh useless during the summer season when dry heat checks the adobe and makes the ground generally porous. Nevertheless, the value of carbon bisulphide, especially for sanitary purposes, can not be easily overestimated for work in the country during the fall, winter, and spring seasons.

Fumigants in general are effective. They possess no marked or peculiar advantages as special weapons against rodents. Their use is limited chiefly to warehouses, elevators, and ship holds. They are deadly to rats in the same way that they are fatal to every sort of life. Many difficulties and some dangers stand in the way of their use. It is safe to advise that no one unacquainted with their action should ever employ fumigants.

NATURAL ENEMIES.

The war upon rats carried on in San Francisco has proved the great value of cats and dogs as natural enemies of the rat. That city now has a law requiring all structures of 800 or less square feet and outside certain limits to be raised high enough above the ground to allow access to cats and dogs. (All other buildings in the city must be rat proof.) An index to the worth of rodent foes in their extermination points from what happened during the great London plague. At that time the disease was supposed to be air carried; any furry material might hold and spread infection. The magistrates decreed that all cats and dogs should be killed to prevent plague from lodging and traveling in their hair. Rats were thus free to live and breed unmolested, and live and breed they did until the plague killed them off; then and then only did the disease cease its ravages among human beings.

DOGS.

Slight training will make excellent ratters of Fox, Irish, or Scotch terriers. Fox terriers have proved especially valuable as retrievers when shooting squirrels, which in one case out of five will escape to their burrows unless sharply retrieved.

CATS.

Cats are little less valuable than dogs against rats, while they are useless against squirrels. The ordinary cat is too well fed to attack large rats and goes, almost solely, after mice.

All other animals naturally preying upon rodents class with wild life—weazels, ferrets, badgers, skunks, and minks. These can be used only in country places, where, however, their raiding of chicken coops tends to counterbalance their value as ratters. The skunk alone is an infrequent slayer of fowl, whereas he harvests innumerable farm pests from worms to crickets. Yet an insurmountable prejudice against skunks stands in the way of realizing his full usefulness against rodents. In addition, various hawks and most owls kill off rats. Since rats come out chiefly in the nighttime, owls have the better chance to be serviceable in their destruction. The efficiency of these birds in rural districts quite equals that of a dog against rats, while besides dogs we have not as yet found a safe natural foe of ground squirrels.

But all such attacks upon rats fail of absolute eradication. One must make it impossible for them to find sustenance and must destroy not only all existing rat houses, but also all chance of their digging or finding new ones.

CUTTING OFF THE RAT’S FOOD SUPPLY.

This is important not alone for its effect in a campaign upon rodents, but equally because it necessitates sanitary care and cleanliness in handling foodstuffs intended for humans and garbage coming therefrom. Abattoirs and places where cattle and hogs are fattened perhaps furnish the greatest number of rats. Stables, food-supply stores, groceries, meat, fish and vegetable markets, restaurants, bakeries, and the various places where food is prepared for human consumption are usually infested. In each of the places the barriers vary according to the nature of the premises. Rat-proof receptacles for the foodstuffs must be installed wherever practical. In San Francisco an ordinance requires every stable to have metal lined feed bins. Markets and places where eatables are constantly being shifted about must be properly screened against rats. Screening should be of heavy wire and sufficient fineness, not larger than halfinch mesh. In all places the food has to be raised such a height above floorings as to be beyond the rat’s reach. This applies also to corn and grain cribs in the country. Yet, no matter how carefully the bulk of the food may be kept from rats, negligence in handling it, in spilling or scattering small amounts upon floors or the ground, will nullify every precaution.

No less painstaking must be the disposition of garbage. Ordinance now requires that all premises in San Francisco be provided with “sanitary garbage cans.” Preferably these should be of zinc or galvanized iron and fitted with tight covers. Under no circumstances should the cover be allowed to remain off its can. Garbage is to be placed in a can without delay and care must prevent the dropping of it upon the ground. Rats once served communities as scavengers; wherever the scavenger work is laxly done, rats are welcomed. Finally, garbage must never be allowed to accumulate and should be removed daily, not less often than every other day.

Special conditions, closely related to the next topic, are encountered in large warehouses and grain sheds. Places where large quantities of food may be stored for a length of time should be constructed of reenforced concrete to be rat proof. Then, again, where vessels are changing cargoes, rat-proof compounds should be erected for the temporary storage of freights. The water fronts of seaports are invariably rat ridden; and in San Francisco a compound for freight held in transit was found invaluable. No effort can be spared in keeping rats from their food if their extermination is to be accomplished.

With regard to ground squirrels, the use of poisoned wheat very properly enters here. With the changing season ground squirrels change their habitat and food. During early spring these rodents come down from their winter dwellings in the hills and seek burrows in meadow lands and cultivated spots. Months have passed since the squirrel tasted wheat; his fickle appetite betrays him. From the first spring months until harvest time one can kill thousands of ground squirrels by tempting them with poisoned wheat. But so soon as harvest time comes, they seek new growing green stuffs to eat and thereafter, on through winter, poisoned wheat is ineffective.

BUILDING THE RAT OUT OF EXISTENCE.

Most certain of all methods to get rid of rodents is to allow them no place in which to live. San Francisco effects this result through its ordinance, which requires small houses outside certain city limits to be raised so high from the ground that dogs and cats can drive out rats from under them, and which requires all other buildings in the city to be rat proofed with cement or concrete. The latter contemplates foundation walls of concrete or brick sunk at least 1 foot to 18 inches to 2 feet above that surface; the whole ground area inclosed by their foundation walls must be covered with concrete at least 1½ inches in thickness. Thus the entrance of burrowing rodents is prevented. Even where buildings stand upon rock or hardpan, these requirements should be enforced. Rock may crack, gradual weather decay may cause crevices to be found in it unseen crannies may be found by rodents, and once the rat lodges in rock his nest is virtually unassailable. With hardpan it is even worse, for the rats can burrow in it, with some difficulty, truly, but when nests are impossible elsewhere, necessity will drive rats to find shelter in hardpan, which will protect them quite as well as rock. In the main, these two points of building rats out of existence, though modified, will apply to any structure.

Yet any negligence will overthrow these safeguards. The principle is to allow no opening within which rodents may nest. Plank sidewalks and back yards will continue the rat nuisance even though buildings are amply protected. Carelessness in throwing old boxes into basements or piling old lumber or refuse within reach will supply shelter for rats despite concreted ground area. The precaution must be constant and consistent.

Another important phase is to cut off the rodent migrations. Prevent rats from moving from place to place. Their time-honored highway is through sewers. Modern sewers afford no protection, inviting rodents to live in them as formerly. Scarcely less important, access should be stopped. Catch-basin feeding sewers should be constructed so that rats can not slip through into the mains, or having once gotten in, they can not escape, and hence must drown. Farms are frequently protected against rodent migrations by tin or zinc sheeting sunk into the ground about a foot and a half and standing about the same height above the surface along the fence line.

Finally, as the progress of rodents from place to place within communities must be hindered, so must they be stopped from entering new communities. Railroads and seagoing vessels carry great numbers of rats in freight. The rat-proof compounds above described serve well enough so far as railroads are concerned. With vessels it is a different matter, and one demanding special attention, since the rodent is only too likely to import infection from foreign harbors. All hawsers thrown out to make boats fast should be provided with traps to catch any rat seeking to land along the hawser. San Francisco, about to possess a rat-proof water front, is now building concrete wharves to prevent the landing of rodents. Every port should be safeguarded by stone, concrete, or iron wharves and piers. As a further protection, all ships should have permanent devices, as is now proposed for naval construction. Levy’s system of metal conduits built into vessels promises much in the present world-wide war upon rodents. Rodents must be “built out of existence,” and to eradicate rats for all time we must erect wide systems of municipal fortifications.

NATURAL ENEMIES OF THE RAT.

By DAVID E. LANTZ,

Assistant Biologist, United States Department of Agriculture.

INTRODUCTION.

Undoubtedly the great increase of rodent pests throughout North America is in large part due to a general scarcity of the animals that habitually prey upon them. Since the early settlement of the country persistent warfare has been made on birds and mammals of prey on the plea that they are enemies of poultry, game, and insectivorous birds. Efforts to destroy the predaceous birds and mammals have been greatly stimulated by the payment of municipal, county, and state bounties, and the destruction has gone on until in many sections these animals have nearly disappeared.

The effect of killing off the natural enemies of rodents has been to disturb natural conditions. Rodents multiply so rapidly that they derive an undue advantage in the struggle for existence when their natural enemies are destroyed. The result is noticeable in the increased depredations of rats, field mice, rabbits, and other pests.

The destruction of carnivorous wild mammals and birds by the farmer, hunter, or game preserver is often due to misapprehension. Because one kind of hawk preys on the farmer’s poultry is not sufficient reason for exterminating all hawks. Nor does the fact that occasionally an owl or a skunk destroys a chicken or a game bird justify warfare on all owls and skunks. It is the occasional individual and not the species that offends.

ANIMALS THAT DESTROY RATS.

The usefulness of the natural enemies of the rat must not be overlooked in plans for its repression. Among the more important are the larger hawks and owls, skunks, foxes, coyotes, weasels, minks, and a few other wild mammals; as well as cats, dogs, and ferrets among domestic animals, and snakes and alligators among reptiles.

HAWKS.

Most of the larger hawks destroy rats. Feeding only in the daytime, they seldom find their quarry near houses and barns, where rats do not venture out until after sunset. Besides, owing to persecution by farmers, hawks generally keep away from farm buildings. In the open fields, however, where rats feed in early morning and late afternoon, hawks find many of the rodents.

The species of hawks that more commonly feed on rats are the buzzard hawks, including the red-tailed (Buteo borealis and sub-species), the red-shouldered (B. lineatus), the broad-winged (B. platypterus), and the Swainson (B. swainsoni); the rough-legged hawks (Archibuteo), two species; and, to a less extent, the marsh harrier (Circus hudsonius), and a few other species.

The writer has several times found the remains of rats about the nest of the red-tailed hawk. Of the 562 stomachs of this species examined by Dr. A. K. Fisher, of the Biological Survey, less than 10 per cent contained poultry or game, while more than 70 per cent contained injurious rodents. Most of the other species of buzzard hawks made a better showing even than this, especially the Swainson hawk, which had fed entirely on harmful rodents and insects. The stomachs of rough-legged hawks examined nearly all contained harmful rodents and none of them contained remains of birds of any sort.

Footnote AH:

Hawks and Owls of the United States, p. 62, 1893.

A few months ago, while walking on the Potomac flats near Washington, the writer met some boys who had just shot a red-tailed hawk. Its crop was greatly distended, and later examination showed that the bird had recently eaten an enormous brown rat. Although the shooting was contrary to law, when it was reported to the nearest policeman, his comment was, “Oh, a hawk! Why, it’s a good thing to shoot a hawk.” The incident illustrates the general popular prejudice against all hawks.

OWLS.

Because they hunt by twilight and at night, owls are more efficient than hawks in destroying rats. All American owls, except the more diminutive species, prey on the common rat. Even the little screech owl (Otus asio) feeds on young rats.

Of all our species, the barn owl (Aluco pratincola) is preeminent as a destroyer of rats. It lives commonly about farm buildings, sometimes even making its nest and rearing its young in the pigeon loft without molesting the pigeons. In such surroundings its opportunities for securing rats are excellent, and no other wild bird is so useful on the farm. The late Henry Newman once stated that every barn owl is worth £5 a year to the British nation, and the value of the bird to the American farmer is not less.

Owls, hawks, and other birds of prey that swallow their quarry whole or in large pieces do not digest the bones, fur, and feathers. They eject these indigestible parts in the form of large pellets, in which the fur or feathers surround the bones. The contents of these casts are an excellent index of the food of owls. Dr. A. K. Fisher, of the Biological Survey, has examined 987 pellets of a pair of barn owls that live in a tower of the Smithsonian building in Washington, and in them found the skulls of no fewer than 192 rats (Mus norvegicus), together with those of 554 common mice and 1,508 field mice (Microtus pennsylvanicus).

Dr. John I. Northrop found a nest of the barn owl on Andros Island, Bahamas. It contained two young owls and the remains of a black rat (Mus rattus). The ground about the nest was covered with pellets which contained remains of the black rat and no other species.

Footnote AI:

The Auk, vol. 8, p. 75, 1891.

The great horned owl (Bubo virginianus) is the largest of our resident owls. It feeds mainly on rodents, though occasionally it takes a fowl found roosting in an exposed situation, as on a fence or in a tree. While it occasionally destroys game birds, the rats it captures would probably destroy ten times as much game as the owl. Charles Dury, of Ohio, in 1886 published a letter from O. E. Niles in which it was stated that he counted 113 dead rats at one time under a nest of this bird.

Footnote AJ:

Jour. Cincinnati Soc. Nat. Hist., vol. 8, p. 63, 1886.

The snowy owl (Nyctea nyctea) is a rather rare winter visitor in the northern United States. It usually arrives when the ground is covered with snow and ordinary food is scarce. Near barns, outbuildings, and stacks it finds its chief subsistence in the common rat; and, if undisturbed, will stay for several weeks in the same locality, destroying many of the pests. Unfortunately, mounted specimens of this beautiful owl are so much in demand that the majority of them fall a prey to the specimen hunter and the taxidermist. The destruction of this bird should be prohibited under heavy penalties.

The barred owl (Strix varia), the long-eared owl (Asio wilsonianus), and the short-eared owl (Asio flammeus) all destroy some rats; but as they do not generally nest or live in the vicinity of farm buildings, the rodents they capture are taken chiefly from the fields. Occasionally a short-eared or a long-eared owl makes its winter home in a group of evergreens near the farm buildings, and does excellent service in clearing the premises of rats and mice. Evergreens are desirable about a country place, if for no other reason than that they attract owls.

The practice of indiscriminately destroying hawks and owls should be discouraged. Game preservers especially should realize that the birds of prey they kill would, if allowed to live, destroy rats, which in the course of a year do many times as much harm to game as the supposed offenders do. Besides, the birds would destroy also large numbers of mice and injurious insects.

The farmer and the poultry grower may easily learn to recognize the few harmful species of hawks, and should confine their warfare to these. The practice of setting pole traps for hawks and owls is exceedingly reprehensible, as it results chiefly in the destruction of our beneficial owls when they come about the premises at night in search of rats. Furthermore, the beneficial hawks and owls should have legal protection. The larger hawks, nearly all of which are beneficial, are slow of wing and much more likely to be shot than the swifter and more harmful falcons.

NATIVE WILD MAMMALS.

Not many species of wild carnivorous mammals live where the common rat is abundant. Coyotes, foxes, and a few others occasionally find a rat in the fields, but for the most part they depend for food on native wild rodents and other animals. Chief among the mammals that do good work in destroying rats are skunks, minks, and weasels.

SKUNKS.

Skunks are excellent ratters, and when they take up their abode on the premises of the farmer, they speedily destroy or drive away all rats and mice. This statement applies equally to the large skunks (Mephitis) and the little spotted skunks (Spilogale). Unfortunately, skunks are seldom allowed to tenant the premises without being molested by either dogs or men. When undisturbed, they are inoffensive, and will stay about the farm buildings or stacks until rats and mice are no longer to be had for food.

Skunks usually hunt by night, and hence poultry properly housed is safe from them. The larger skunks do not climb, and can capture only fowls that roost on the ground. Indeed, so few skunks ever learn to kill poultry that there is no good reason for warfare on the skunk family. Besides destroying mice and rats, the animals are invaluable as consumers of noxious insects, especially cutworms, army worms, white grubs, May beetles, grasshoppers, crickets, and sphinx moths.

WEASELS.

Weasels are good ratters and mousers. Several of our species come about buildings, and often perform excellent service in destroying rats and mice. They are more likely than the skunk to attack poultry, for they can enter the poultry house through smaller openings. At times weasels seem to kill for the mere love of killing, and while occasionally this trait makes them formidable in the poultry house, it also renders them more efficient as destroyers of rodents. A small weasel can follow a rat into all its retreats, and will soon clear a stackyard or shed of all rodents.

Our largest weasel, the black-footed ferret (Putorius nigripes), occasionally deserts its wild haunts on the plains and comes about buildings in search of rats and mice. In 1905, while the writer was at Hays, Kans., one of these ferrets took up its quarters under a board sidewalk in the business part of the village. The squealing of the rats it killed was often heard.

As regards the destruction of poultry by weasels, the same care necessary to exclude the rat from a poultry house will keep out the weasel also. When so excluded, a weasel will do no harm about the premises, but may be depended upon to drive out or kill all the rats and mice.

MINKS.

Minks are excellent ratters, but as enemies of poultry are worse than weasels. They destroy fish also. The great demand for mink fur causes close trapping of these animals, and in the future they are not likely to influence greatly the numbers of rodent pests.

DOMESTIC ANIMALS.

Among the enemies of rodents often employed as aids to rat destruction are the dog, cat, and ferret.

DOGS.

The value of dogs as ratters can not be appreciated by those who have had no experience with trained animals. The ordinary cur and the larger breeds of dogs seldom make useful ratters. Small Irish, Scotch, and fox terriers, when well trained, are superior to most other breeds as ratters, and under favorable circumstances may be depended on to keep premises free from rodents. Much, too, may be done by the farmer or householder to increase the effectiveness of his dogs by removing obstructions to their work. Corncribs and outbuildings, when of wood, should not have floors close to the ground, but should have ample room below to permit dogs to move about freely.

With a little preliminary training, most terriers learn to hunt rats independently, and they thus become doubly useful on farms and in warehouses.

CATS.

When the black rat was the dominant species in Europe and America, cats were the chief dependence of the householder against rats; but comparatively few cats will venture to capture a full-grown brown rat. Then, too, the ordinary house cat is too well fed and consequently too lazy to be an efficient ratter.

Occasionally, however, one meets with rat-killing cats whose work in destroying the brown rat has decided value. These cats are rarely of the fine breeds, but generally of the common “tabby” variety, kept in barns or warehouses, fed on milk, and left to forage for their own meat. Managed in this way, cats are far less objectionable on sanitary grounds than when kept in the house as pets. In the country, on the other hand, barn cats are far more likely than the house-kept ones to run at large and prey upon birds and young poultry. Aside from the rat itself, we have no more serious enemy of birds and game than half-wild cats, many of which have been abandoned in fields and woods by the thoughtless. All things considered, cats do not rank high as destroyers of the common brown rat.

FERRETS.

Tame ferrets, like weasels, are inveterate foes of rats, and can follow them into their retreats. Under favorable circumstances ferrets are useful aids to the rat catcher, but their value is often greatly overestimated. They require experienced handling and the additional services of a well-trained dog or two to do effective work. Dogs and ferrets must be thoroughly accustomed to each other. A noisy or excitable dog is useless in ferreting. The ferret should be used only to drive out the rats, which are then killed by the dogs. If an unmuzzled ferret is sent into rat retreats under floors, it is apt to lie up after killing a rat and sucking its blood. Sometimes the ferret will remain for hours in a rat burrow or escape by unguarded exits and be lost.

Such experiences often discourage the amateur ferreter. Besides, ferrets are subject to diseases and require the greatest of care as to their food. For these reasons the use of ferrets to destroy rats, except in the hands of the experienced, is generally expensive and disappointing.

OTHER ANIMALS.

MONGOOSE.

The various species of mongoose (Herpestes and Mongos) are destroyers of rats, and their importation into this country has often been urged. Many years ago they were introduced into Jamaica and Hawaii to save the sugar plantations from ravages by rats. The mongoose has, however, proved very destructive to native birds and poultry in the islands, and its introduction is now generally regretted. Its importation into the United States is prohibited by law.

ALLIGATORS.

In the South the alligator is said to destroy many rats along levees and banks of streams, and its protection has been urged on this account.

SNAKES.

Our larger snakes are beneficial in destroying rats, mice, prairie squirrels, and pocket gophers. As most of the food of snakes is obtained remote from human abodes, only a small percentage consists of rats.

BOUNTIES ON PREDATORY ANIMALS.

Whatever may be said in favor of bounties on the larger beasts of prey, those on hawks, owls, and the smaller fur-bearing animals can not be justified. Payments of this sort should cease, and laws should be enacted to protect species which careful investigations have shown to be mainly beneficial.

A few States still pay bounties for the destruction of foxes, weasels, skunks, minks, and raccoons. All of these, except the southern weasels, have valuable fur, and hence should be protected as a source of wealth. In addition they do far more good by destroying rats, mice, and other field pests than harm to game and poultry.

The payment of bounties on hawks of any kind is open to the objection that officials hardly ever discriminate between the harmful and the useful kinds, even when the statutes do so. Since the beneficial kinds are the more easily captured, public money is often paid out to reward what really injures the community. The bounty on owls is still more reprehensible, since owls are a more decided check to rodent increase.

The natural enemies of the rat exercise a steady, cumulative effect in restricting the numbers of the pest. That the effect is not greater is largely our own fault, since instead of protecting the birds and mammals that prey on the rat, we destroy them, sometimes even offering bounties on their heads. In future our aim should be to increase their numbers and to protect them in every way possible.

RAT PROOFING AS AN ANTIPLAGUE MEASURE.

By RICHARD H. CREEL,

Passed Assistant Surgeon, United States Public Health and Marine-Hospital Service.

To appreciate the great importance and absolute necessity of rat proofing as an antiplague measure, it is only necessary to consider the results that have followed its use as compared with other measures that have been relied on in recent years in combating this disease. These were, briefly, disinfection, evacuation, or destruction of buildings in infected areas, preventive inoculations, and destruction of rats either by poison or by trapping.

Plague was formerly believed to be communicable by aerial transmission and through the agency of fomites. Sanitarians have, therefore, put great faith in disinfection procedures, but the results have never been satisfactory, and it is only necessary to consider the method of transmission of plague to perceive the fatuity of bactericidal measures. Measures intended for the destruction of fleas are also of relatively small value. It is well worth while to destroy all fleas possible, but if those infesting the rat population escape, the efforts will have had little effect in preventing the spread of plague. It is only those fleas that infest rats and their habitats that are of importance in relation to the transmission of disease, and it is only by rat proofing that their destruction in rat burrows and runs can be accomplished.

Rat-proofing of individual buildings is of no recent date, but new emphasis was laid on rat-proofing as a separate and distinct antiplague measure by Passed Assistant Surgeon Mark J. White in an article written in the fall of 1907.

Footnote AK:

Journal American Medical Association October 19, 1907.

Disinfecting procedures must be regarded as of minor importance in plague prevention, except in pneumonic cases where its use is imperative. It is not intended to depreciate the value of disinfection, but rather to estimate its exact value as an antipest measure. Time and money should not be wasted nor a feeling of false security engendered by using an ineffective measure when others, as rat proofing, of much greater value are at hand. As an example of this might be cited an outbreak of plague in one of the refugee camps during the recent epidemic of the disease in San Francisco. This camp covered several blocks and housed between two and three thousand people. The camp grounds throughout and the houses were disinfected and disinfected well. At the same time, every effort was made to poison and trap rats. Notwithstanding these precautions, cases continued to occur, but when the houses were elevated there followed an immediate cessation of plague cases in the camp.

Another case of infected premises proved equally refractory to disinfection. The place was a large two-story frame dwelling located in the center of the city and in a good neighborhood. The yard was planked, as was also a part of the basement, the latter being used as a storeroom. On November 1 there occurred in this dwelling a fatal case of human plague, and plague rats were found at the same time. The place was disinfected in the usual manner and thorough measures were taken to trap and poison rats with apparent subsidence of infection, but on January 22 a plague rat was trapped, followed by another on January 31, after which the occupant of the building vacated it in great alarm. All planking was then removed from the yard and basement and concrete substituted by the owner, the place thereby being rendered thoroughly rat proof, and no plague rats were subsequently taken from that dwelling or in its immediate neighborhood.

In 1902 the plague outbreak was almost wholly confined to the Chinese colony. Chinatown was made the battle ground, and among other measures rat proofing was enforced, with the result that after the fire it was by far the most sanitary district in the city of San Francisco from a structural point of view. The buildings when erected were made rat proof from cellar to garret. The Chinese had had their lesson, and to their credit it must be stated that they responded with a greater show of intelligence than did some of the residents in surrounding districts.

Adjacent to the Chinese colony is the Latin quarter. In the rebuilding of this section, no attention was paid to rat proofing; consequently many of the buildings consisted of small shacks set on the ground or abutting some insanitary stable, and were therefore ideal rat harbors. On account of these conditions the natural results followed. Chinatown, on the other hand, which had contributed in the previous epidemic almost the entire number of plague cases during the epidemic of 1907, did not furnish more than two or three of the plague cases reported; that is, less than 2 per cent of the total cases reported, while the Italian colony, including North Beach district, probably furnished over 50 per cent of the total.

The evacuation or burning of buildings can hardly be called a successful measure any more than a retreat can be styled a victory; moreover, there can be no question from an economic standpoint as to the value of rat proofing over abandonment except in a few isolated cases of dilapidated insanitary property.

Schemes and plans for demurization, total or partial, have been as numerous and varied as they have been unsuccessful. Traps and poisons have been the agencies of destruction, but until some highly communicable epizootic peculiar to rodents shall have been discovered, absolute eradication of the rat can be considered as nothing less than impossible.

A recognized authority on plague, Major Morehead, of the Indian Medical Service, states that “rat destruction is of doubtful value,” referring, of course, to trapping and poisoning when those measures are used solely without auxiliary measures. He agrees with Japanese authorities in their arguments that as rat populations decrease, the breeding rate among survivors increases, due, obviously, in part at least, to increased food supply and harboring facilities. Such a result is assured where rat proofing is not accomplished at the same time. This latter procedure, by destroying rat harborages and cutting off food supplies bring about conditions unfavorable to breeding.

The total eradication of rats in a locality is not absolutely necessary, however, to the eradication of plague. If the rat population is kept within fairly low limits, rat centers destroyed, and such rat population as does exist well scattered and not congested, it is ventured that rat plague will disappear from a locality. Plague among rats in San Francisco ceased to appear when the number of rodents was reduced some 50 per cent, but such reduction was accomplished only after six months of ceaseless endeavor, which included also the rat proofing of the bakeries, stables, and markets in the city.

It is a logical supposition that close contact is just as essential for the propagation of plague among rats as it is for the spread of certain communicable diseases among human beings, the increase of cases being in direct proportion to the density of population and closeness of contact.

RAT PROOFING OF PRIMARY IMPORTANCE.

Without the general enforcement of rat proofing antiplague measures are bound to be more or less temporary and decidedly unsatisfactory. This subject is of immense importance to the public, both from a sanitary and a commercial standpoint, but the latter aspect of the question is more apt to prove of interest to most communities.

The measures necessary to render buildings rat proof are the same, however, whether they be instituted for sanitary or for commercial reasons. Rat proofing will, therefore, be considered entirely from a sanitary standpoint; but it can be understood that granaries, bakeries, butcher shops, packing houses, dwellings, and other places, if rat proofed for sanitary reasons, are just as much protected from depredation of the rat as though the work had been performed for commercial reasons alone.

Rat proofing has a twofold objective. It serves as a protection to the inmates of a building, and excludes rodents from sources of food supplies and harboring places. While rat proofing should be enforced as a general measure in all plague-infected localities, it is imperatively demanded in premises whereon have occurred cases of human or rodent plague.

Plague-infected localities or places that contain food must be rendered impervious to rats in order to insure the success of other preventive measures. Rats can be trapped or poisoned only when other food supply is excluded. A rat will enter a trap for food or will eat poisoned preparations not because of their greater attractiveness, but because of their greater availability. It therefore follows that rat proofing of food supplies is a prerequisite to success in rat eradication. The food depots requiring attention in the order of importance are stables, meat markets, bakeries, restaurants, groceries, warehouses, and private dwellings.

It is logical to suppose that the most common mode of infection is by reason of plague rats dying in the walls, roofs, or floorings of human habitations. As soon as the rat’s body is cold the fleas abandon it for another rat, some domestic animal, or human being. The risk to human inmates in such infected houses, therefore, is evident.

That rat proofing is a valuable measure is shown by the reports of the British Plague Commission where are mentioned the results following the use of rat-proof “go-downs” and those not so constructed. Additional evidence is presented by the fact that appalling epidemics of plague have ravaged India and the China coast, whereas in the Philippine Islands but few people die of the disease. It would appear that the comparatively few cases in the Philippine Islands were due to the fact that most Philippine dwellings are rat proof by reason of being elevated from the ground and the fact that the walls are thin and offer no refuge whatever to rats.

RAT PROOFING IS EXPENSIVE.

The almost insuperable obstacle that will usually confront the sanitary authorities in such work will be either the financial inability of the unfortunate community or the sordid unwillingness to make any expenditure that does not promise personal gain.

When the influence of the mosquito in the transmission of yellow fever was proven, recourse was had to mosquito proofing of both the sick and the well as a preventive measure. Rat proofing in plague is just as rational and necessary, but the financial expenditure contemplated thereby has been of such proportion as to cause the majority of sanitary authorities in different parts of the world to dismiss the idea as impossible.

To properly rat proof a city undeniably requires enormous expenditures, but no antiplague campaign was ever waged without an immense outlay of both money and labor. If allowed to progress unchecked, however, plague, either through ravages of the population or through commercial interference, is ruinous. To fight plague, therefore, is the only alternative, and a costly campaign should be anticipated and prepared for in advance. To merely put out traps and poisons without the preliminary rat proofing required can be productive of little good and no permanency. Such a plan of campaign may be attractive because of its relative cheapness, but any city or country that relies wholly on such measures is practicing false economy and deferring the day of reckoning.

It becomes evident, therefore, that rat proofing is of the greatest value as an antiplague measure, and that practical results to be expected are much greater than with any other method.

As has already been stated, the individual premises on which plague either among rodents or human beings has occurred demand first and immediate attention. The work should be extended as rapidly as possible from the point of infection so as to include the entire block and neighboring blocks.

While the chief energies should be centered on plague-infected foci, similar work should be carried on simultaneously throughout the city.

METHODS OF RAT PROOFING.

If plague occurs in the grounds of dwellings the following course should be pursued: All planked-over areas, including sidewalks, that might possibly shelter a rat should be removed, leaving either bare ground or, at the option of the owner, gravel or concrete used, the gravel being preferable. Small sheds should be elevated, or their ground floors concreted. Wood sheds should probably be left without flooring, wood kindling or other contents being piled on elevated platforms provided for the purpose. Stables on the premises should be treated as indicated in a subsequent paragraph relating to these structures.

The garbage depository must be given most careful attention. It should be a metal receptacle, preferably a galvanized can, water-tight to prevent seepage which would attract rats, and there should be a closely fitting lid. A can 2 feet in height without cover will not be proof against the incursion of rats.

The rat proofing of chicken yards is a difficult task as most chickens in private families are fed on table scraps, thereby attracting and supporting a fair quota of rats. The entire inclosure should be protected by wire fencing 6 feet high and of a mesh not larger than a half inch. Ordinary poultry netting is inadequate, the mesh being too large. The edge of the yard should be of concrete construction, the concrete extending 1 foot upward and 2 feet inward. If, on any subsequent inspection, rats have been found to have burrowed into the inclosure, the entire area should be concreted, sand or earth being allowed as a top dressing.

It would seem sufficient to confine these specifications to a feeding pen, but in practice this will not suffice, as a mere pretext of such a place would be built, and the housewife would continue to throw scraps into the unprotected yard.

The dwelling house itself should receive the most careful attention. If it is a small frame structure the cheapest and most effective means of rendering it free from rats is by elevating it, the minimum height being 1½ feet, measured from the most dependent joist. At the same time, all underpinning should be freed of rubbish or other material. It is not sufficient to raise the structure a few inches so as to permit the entrance of cats and other enemies of the rat. Such height and exposure must be secured as to deprive all rodents of cover.

If the house is of more substantial structure, and always if it has a cellar or basement, concrete or some other rat-proof material should be adopted. If sound foundation walls of stone or brick exist, then only the addition of a concrete floor is necessary. The stopping up of rat holes in any substance pervious to rats is at best a poor expedient.

The grounds must be rendered rat proof by piling all loose materials at such an elevation as will preclude rat harborage. All rubbish should be burned or otherwise destroyed. All basement windows should be properly protected against the ingress of rats, and if the Mus rattus be present, even second and third story windows should not be considered too high to afford them entrance.

All loose materials on the premises should be properly piled, even though they are in a rat-proof cellar. It is not probable that the Mus decumanus would remain or breed in any place where it could not burrow; but no encouragement should be offered to any rodent let in by carelessly left open doors. There have been cases where the black rat has lived, increased, and overrun a house which was structurally rat proof, but in which there was allowed easy access through open windows and doors, and great piles of loose materials and dunnage furnish harborage.

Stables are of twofold importance because they provide a source of food supply for rats and furnish harborage. All grain must be kept in a metal lined box or granary. A small stable is sufficiently rat proof if it has an elevation of 2 feet with clear underpinning, provided the floor is rendered impervious to falling grain. Barns of larger extent are best made rat proof by concrete flooring tight on the ground, and the area walls should be of concrete 1 foot high or of galvanized iron of standard thickness. The ingredients of concrete should be specified as to quality and quantity.

The windows of stables should be screened, especially if black rats be present. To render a large livery stable rat proof, however, is hardly practicable, owing to doors being open almost continuously, but rat proofing even in such buildings will destroy rat harborage and limit rat invasions to an occasional migratory rodent. With concrete flooring and protected feed pens it should be an easy task to keep such a building free from rats.

Finally, manure pens should be rat proof or the manure thrown into the corner of the rat-proof stable, provided there is frequent cartage.

RAT-PROOFING ORDINANCES SHOULD BE SPECIFIC.

Any law or ordinance providing for rat proofing should specifically state the minimum thickness of concrete and cement. Concrete 4 inches deep with one-half inch dressing of cement or 1-inch asphalt answers very well. Area walls if of concrete should be 6 inches thick, and the floors should have sufficient slant to allow drainage.

Any expedient as galvanized iron sunk into the ground and made flush with the flooring will not prove of practical value, as it allows rat-harboring space to exist beneath the flooring, and sooner or later rats will gain access thereto by burrowing under the iron gratings or through the wooden flooring.

Meat markets should have concrete floors with cement or asphalt dressing, the floors to be close on the ground and surrounded by properly constructed foundation walls of stone or brick in cement. Water-tight metal cans should be provided for all scraps, and especially for the sawdust with its admixture of fine pieces of meat.

Bakeries and restaurant kitchens should be treated in the same way as meat markets. Packing houses, slaughter pens, warehouses, and food depots in general should be concreted.

The water front demands the greatest attention. The piers and wharves should be of concrete or steel construction. The shipping should be shored off from the dock, and all lines properly rat guarded. When not in use, gang planks should be lifted. Notwithstanding these precautions, rats will be imported from time to time, and the only practical way to prevent their getting ashore will be the systematic and routine fumigation of ships by the quarantine authorities.

The rat proofing of sewers is open to argument. Of all places in a city the sewer is certainly the one where rats can die with the least danger to the human population. For this reason the sewer should be the last structure in a municipality to be made rat proof. The movements and migrations of rats should be controlled to the extent of making corner catch basins their sole means of entrance and exit to sewers. The small and large iron-pipe mains require no attention in this respect, but where mains are constructed of brick, and especially where they are old and in bad repair, they should be repaired, all rat runs leading from the sewer walls being stopped up and all blind sewers being closed. By this means there will be prevented the breeding of rats in these areas.

The rat proofing of catch basins by any method that would not also block the entrance to the basin seems hardly possible. Properly trapped basins, however, will be found almost as effective and just as desirable.

To attain efficient rat proofing requires necessary laws or ordinances and public sentiment favoring their enforcement. Dead-letter laws that form no small part of many city statutes attest the fact that favorable public opinion is almost indispensable to their enforcement. However, well-drafted laws, clear and specific in requirement and impartially and consistently enforced, inevitably lessen and destroy opposition.

In the foregoing are contained general principles necessary to rat proofing in the case of an outbreak of plague. Due allowance will have to be made, however, for local conditions, and special considerations as they arise, as no unvarying plan will be practical of application in every instance.

CHOICE OF ARCHITECTURE AND BUILDING MATERIALS.

Cities and countries have from time to time wholly revolutionized their type of buildings and constructive materials for either commercial or æsthetic reasons. It is suggested that ports having trade relations with countries where plague prevails should bear in mind the advisability of taking advantage of this fact and revise their building laws with the view to rendering all new buildings rat proof.

Concrete has been advocated for purposes of rat proofing because of its durability and relative cheapness. Concrete flooring or side walls can be made more durable, however, by embedding therein steel netting of 1 or 2 inch mesh. By this method the cost of construction will probably be reduced, as a thinner layer of concrete would be sufficient, and the metal would be protected, thereby adding stability. Such construction at the same time would be doubly rat proof.

THE INEFFICIENCY OF BACTERIAL VIRUSES IN THE EXTERMINATION OF RATS.

By M. J. ROSENAU,

Surgeon, U. S. Public Health and Marine-Hospital Service, Washington, D. C., now Professor of Preventive Medicine, Harvard University Medical School.

INTRODUCTION.

Rats are notoriously resistant to bacterial infections. About the only exception is the plague bacillus. Plague among rats occurs both in endemic and epidemic form. When we recall that this virulent disease, which spreads readily from rat to rat, neither eradicates these rodents nor, as a rule, makes any appreciable inroads on the number of rats, we can hardly expect that an artificially induced bacterial disease would be successful. No other known bacterial infection has such a virulence for rats as the plague bacillus has maintained. Epizootics of bacterial nature, therefore, can not be classed among the natural enemies of the rat. Despite this fact persistent efforts have been made to create artificial epizootics to combat these dangerous and destructive rodents, but with little success.

The bacterial viruses that have been used for the destruction of rats and mice belong to the colon-typhoid group and excite enteritis of different characters and a septicemia.

Footnote AL:

More particularly the hog-cholera group, which includes the para-typhoid organisms.

In 1889 Loeffler discovered and described a bacillus which he called the bacillus of mouse typhoid (B. typhi murium). He isolated this organism from a spontaneous epidemic which occurred among white mice in the Hygienic Institute at Griefswald. He determined that this bacillus not only caused the death of his mice in the laboratory, but also that the infection was taken into the system of the mouse by ingestion. He found the cultures to be especially virulent for field mice (Arvicola arvalis). Loeffler gives a complete description of the bacillus which, from a biologic standpoint, is the parent stock of almost all subsequent work along this line. The bacillus used by Danysz and other workers is either identical with or very closely allied to Loeffler’s bacillus of mouse typhoid.

Footnote AM:

Loeffler, F.: Ueber Epidemieen unter den im hygienischen Institute zu Griefswald gehalten Mäusen und über die Bekämpfung der Feldmausplage. Centblt. f. Bakt., Orig., vol. 11, 1892, pp. 129–141.

In 1892 Loeffler personally undertook a campaign against the field mice in Thessaly and reported satisfactory results. The depredations carried on by the mice were checked within eight to nine days.

Footnote AN:

Loeffler, F.: Die Feldmausplage in Thessalien und ihre erfolgreiche Bekämpfung mittels des Bacillus typhi murium. Centblt. f. Bakt., Orig., vol. 12, 1892, p. 1.

The English commission threw doubt upon the Thessaly operations and concluded that the bacillus as a means of destruction of mice has no value. They found the method to be expensive, affecting only one species of mice; further, that the epidemic-like spread of the disease in the fields was not sufficiently investigated, and that the infected material retains its virulence only for eight days and does not permit of being used in continued bad weather.

Footnote AO:

Wien. landw. Zeit. 1894, p. 783.

Loeffler’s optimistic report, however, stimulated many similar trials with varying success. Practically all these efforts were directed against mice, until 1900, when Danysz took up the subject from the standpoint of the rat and plague.

Danysz found that Loeffler’s Bacillus typhi murium proved to be pathogenic for ordinary mice (Mus musculus) and for field or harvest mice (Mus arvicolis), but not for rats.

The culture isolated by Laser in 1892 was pathogenic for field mice (Mus agrarius); this organism killed 70 of the 76 mice which were used as experiment animals at the Hygienic Institute at Königsberg.

Footnote AP:

Laser, Hugo: Ein neuer für Versuchsthiere pathogener Bacillus aus der Gruppe der Frettschen-Schweinseuche. Centblt. f. Bakt., Orig., vol. 11, 1892, p. 184.

Mereshkowsky in June, 1893, isolated an organism belonging to this group from a ground squirrel known as the Zisel (Spermophilus musicus). This culture killed domestic and field mice when placed in their food, but was not pathogenic for rats.

Footnote AQ:

Mereshkowsky, S. S.: Ein aus Zieselmäusen ausgeschiedener und zur Vertilgung von Feld-resp. Hausmäusen geeigneter Bacillus. Centblt. f. Bakt., Orig., vol. 17, 1895, p. 742.

The Japanese investigator Issatchenko, in 1898, briefly described a bacillus obtained by him from gray [white?] rats, which proved virulent for rats and mice.

Footnote AR:

Issatchenko, B.: Untersuchungen mit dem für Ratten pathogenen Bacillus. Centblt. f. Bakt., Orig., vol. 31, 1902, p. 26.

Each of these various bacilli is of such variable virulence that it could not be used for the destruction of all species of these rodents.

Danysz therefore conceived the notion that it would be of great interest first to extend the field of action of one of these organisms by increasing its virulence so that it would attack other species of rodents, and then maintain this increased virulence at its highest point.

Footnote AS:

Danysz, J.: Un microbe pathogène pour les rats (Mus decumanus et Mus rattus) et son application à la destruction de ces animaux. Ann. Inst. Pasteur, vol. 14, 1900, p. 193.

In 1900 Danysz isolated a bacillus from a spontaneous epidemic among harvest mice. This organism was a cocco-bacillus presenting the general characteristics of the colon-typhoid group and resembling the bacillus of Loeffler—B. typhi murium. From the first this bacillus showed a slight pathogenicity for gray rats (M. decumanus). Out of 10 animals fed with a culture of this microbe 2 or 3 would die; several others would sicken and recover; others appeared completely refractory. The fact that a certain number of the rats fed with these cultures always succumbed led to the hope that it would be possible to increase the virulence of this particular microbe by the generally accepted methods—that is to say, by a certain number of passages from rat to rat.

Danysz first tried to increase the virulence of the organism by this means, but he found that successive passages from rat to rat, whether by feeding or by subcutaneous injection, ended by enfeebling rather than increasing the virulence of the microbe. He found that it was rarely possible to go beyond 10 to 12 passages. Sometimes the series was stopped at the fifth passage, or even sooner, by the survival of all the animals undergoing experiment. The result was exactly the same if, instead of alternating each passage through the animal by a culture in bouillon or agar, the bodies of animals dead of a preceding passage were fed to others.

It was therefore plain that in the evolution of an epidemic caused by this microbe it was necessary to take account of the indisputable diminution of the virulence of the microbe, as well as the natural resistance of the survivors.

Passage of cultures in collodion sacs inclosed in the peritoneal cavities of rats was tried, both in interrupted series and by alternating each sac culture with a culture in bouillon or on agar, but the end was invariably a notable diminution of virulence when administered by the digestive tract.

Finally, after long and painstaking procedures, Danysz obtained a very virulent culture that, contained in flasks and kept from the influence of light and air, preserved its virulence for several months. Planted on agar it preserved its virulence without appreciable diminution for two months under laboratory conditions. In bouillon, in flasks, or in tubes stoppered with cotton it altered very rapidly.

DESCRIPTION OF THE ORGANISM.

A culture of Danysz’s virus obtained from the Pasteur Institute had the following characteristics:

The organism is a cocco-bacillus showing distinct motility. Stains well by the ordinary stains, but does not stain by Gram’s method.

It grows well at ordinary room temperature, also in the incubator, and on all the ordinary media. In bouillon it produces a uniform cloudiness in twenty-four hours. A slight scum forms after several days’ growth, which falls to the bottom when shaken. In Dunham’s solution it grows well, but produces no indol in twenty-four hours’ growth.

It does not coagulate milk.

It grows the whole length of the stab in gelatin, forming small whitish colonies in the deeper portions of the tube. It does not grow over the entire surface of the gelatin tube; does not liquefy gelatin.

It grows under anærobic conditions.

It ferments glucose bouillon, but not lactose bouillon. In glucose bouillon it produces 1-CO{2}, 5-H. It also produces H{2}S.

From a general biological standpoint it is plain that this bacillus belongs to the para-typhoid group, and is very similar to the bacillus of hog cholera as well as the Bacillus icteroides, also B. enteritidis, so far as its morphological and cultural characteristics are concerned.

In the following table the fermentations produced by various members of this group upon certain carbohydrates are shown:

─────────────┬────────┬───────────┬────────┬────────┬────────┬───────── Organism. │Lactose.│Saccharose.│Maltose.│Mannete.│Glucose.│Levulose. ─────────────┼────────┼───────────┼────────┼────────┼────────┼───────── B. typhosus │ − │ − │ − │ − │ − │ − B. dysenteriæ│ − │ − │ − │ − │ − │ Shiga │ │ │ │ │ │ B. dysenteriæ│ − │ − │ − │ − │ − │ Kruse │ │ │ │ │ │ B. │ │ │ │ │ │ para-typhosus│ − │ − │ + │ + │ + │ + A │ │ │ │ │ │ B. │ │ │ │ │ │ para-typhosus│ − │ − │ + │ + │ + │ + B │ │ │ │ │ │ B. para colon│ − │ − │ + │ + │ + │ + B. acidi │ + │ − │ + │ + │ + │ + lactici │ │ │ │ │ │ B. hog │ − │ − │ + │ + │ + │ + cholera │ │ │ │ │ │ B. typhi │ − │ − │ + │ + │ + │ + murium Danysz│ │ │ │ │ │ B. icteroides│ − │ − │ + │ + │ + │ + B. │ − │ − │ + │ + │ + │ + enteritidis │ │ │ │ │ │ B. coli │ + │ + │ + │ + │ + │ + communis │ │ │ │ │ │ ─────────────┴────────┴───────────┴────────┴────────┴────────┴─────────

Footnote AT:

Or bubble.

EXPERIMENTS UPON RAT VIRUS IN THE HYGIENIC LABORATORY.

In 1901 I made an investigation of this pathogenic microbe (B. typhi murium) applied to the destruction of rats under laboratory conditions. One hundred and fifteen rats were fed with the cultures in various ways during the course of these experiments with the virus. Of these, 46 died—less than half.

Footnote AU:

Rosenau, M. J.: An investigation of a pathogenic microbe (B. typhi murium Danysz) applied to the destruction of rats. Bull. No. 5 of the Hygienic Laboratory, U. S. Mar. Hosp. Serv., Washington, 1901, 11 p.

Most of the rats used were the gray rat (M. decumanus or norvegicus) and the tame white rat. A few (8) of the wild black or house rats (M. rattus) were used.

The virus is in reality pathogenic for these three kinds of rats when ingested. No special difference was noted in its effects upon the various species.

As the work progressed it soon became evident to me that the result depended largely upon the amount of the culture ingested. By starving rats for a day or two and then giving them all they could be induced to eat and drink of the cultures, a very positive result was obtained. In one instance of 27 rats so fed all died within a week. If the rats are given a small amount the effect is uncertain—only a few die. In one instance I fed 70 rats with 4 agar tubes and only 7 died. Feeding them a second time with very large quantities 9 more died. The survivors were then fed with all they could be induced to eat every day for a week without effect.

It seems plain, therefore, that a large primary dose proves fatal, and a small dose is not only uncertain, but produces an immunity. This is a very important factor, for it is likely that in the wild state rats would often partake of an amount too small to cause death. Such rats may then subsequently eat large amounts of the culture with impunity.

It would seem then that, after all, the virus is not so different from the laying of a chemical poison, depending as it does for its effect upon the amount ingested. A chemical poison, however, does not possess the disadvantage of producing an immunity. Another disadvantage possessed by the virus is the rapid deterioration in virulence which occurs when it is exposed to the action of air and light, or when it becomes dry, as is very apt to happen when laid out for rats in the wild state.

Since these early experiments, tests have been made of various rat viruses in the Hygienic Laboratory, and the results are given in the following pages:

AZOA.

Series 1. Single feeding of azoa in oatmeal. Rats starved twenty-four hours before feeding. Three out of eight animals died in four, five, and seven days, respectively. Micro-organisms resembling the predominant one of azoa could not be isolated from their hearts’ blood. The organs of these dead rats were fed to fresh rats with the result that one of the three died. It must be mentioned that the mortality among our fresh rats was nearly as high as that in the experimental animals from a disease probably due to infection with an animal parasite.

Series 2. Daily feedings with azoa in oatmeal. Five white rats fed with the mixture, a constant supply being kept in the cage. These animals were picked rats freshly obtained from the dealer. One rat died after seven days. It was heavily infested with lice. The azoa organism could not be found in the blood. The rest remained well after twenty-five days.

Series 3. Black tame mice, daily feedings. One of the five died after seven days. The rest remained well after fourteen days.

These experiments indicate that azoa is not pathogenic for white rats and black tame mice to a degree rendering it applicable for vermin extermination on a practical scale, provided that its action is no more pathogenic for the wild than for the tame species.

RATITE.

The manufacturers recommend a single feeding of this substance rather than a continued exhibition of the virus.

Series 1. Five white rats starved twenty-four hours and then fed with a mixture of ratite and oatmeal. Subsequent daily feedings with plain oatmeal. Picked animals fresh from the dealer. One animal died after twelve days; too much putrefied for further examination; had been heavily infested with lice. The remaining rats are well after twenty-five days.

Series 2. Five black tame mice fed as above. Three were found dead after eighteen days and the other two after nineteen days. Further experiments were not made, as putrefaction was too far advanced when they were found. The room in which they were kept had been unusually cold just before their death owing to a sudden and unexpected drop in the external temperature.

Ratite does not appear to be very pathogenic for white rats. All the five mice fed with ratite died in eighteen to nineteen days (much longer than the advertised incubation period of the infection), but their death could be reasonably attributed to unusual cold. This part of the test is therefore invalidated except that the animals lived considerably longer than would be expected from the literature furnished by the manufacturers, which says that the effects of laying the virus will be apparent in eight to ten days.

DANYSZ VIRUS.

Twelve tubes of Danysz virus were sent to the laboratory for examination April 7 by the Independent Chemical Company, agent for Danysz Virus Company (Limited). The label stated “Keep in a cool place and at above temperature; use before May 15, 1909.”

The virus was kept at 15° C. until April 13, when it was turned over to Passed Asst. Surg. W. H. Frost, who made the following tests:

One tube opened. Cultures made on two agar tubes were found to correspond in cultural characteristics with the bacillus of Danysz virus as generally described. The remainder of the tube prepared according to directions in accompanying circular, using stale dry bread 2 ounces and suspension of the culture in normal salt solution.

Series 1. Approximately equal parts, then fed to six white rats in individual cages, they having not been fed for twenty-four hours previously. Rats all ate greater part of infected food.

Five rats of series 1 died within five to seven days and were partly eaten before being removed from the cage. The pathological changes in all cases were chiefly enlargement and congestion of spleen and liver, and in some cases inflammation of small intestine. In each case an organism was obtained, usually in pure culture, from one or more organs, corresponding culturally and morphologically with cultures taken from original tube.

Series 2. April 14: Rats all ate greater part of infected food. Transferred to large cage containing nine other white rats. Nine other white rats exposed to infection by being placed in a large cage with the rats of series 1. Four of the nine rats of this series died in four to seven days after eating infected rats.

Pathological changes and results of cultures from internal organs the same as with series 1. Autopsy and cultures impossible in one case, where body was almost completely devoured.

Series 3. May 5: Three of the six surviving rats (one from series 1, two from series 2) were placed in individual cages, deprived of food for twenty-four hours, then fed each with one-third agar tube cultures of Danysz virus (the same used in the original feeding). All three ate practically all the virus given.

All three of these rats remain alive and well after two months.

Summary.—Series 1. Six rats each fed one-twelfth to one-sixteenth agar culture Danysz virus. Five died within five to seven days.

Series 2. Nine rats exposed to infection by being placed in cage with series 1. Four died within eight to twelve days after death of first rat of series 1.

Series 3. Three of the surviving rats (1 from series 1 and 2 from series 2) fed each with one-third agar tube of original Danysz virus as used in series 1. None died.

TRANSATLANTIC RATIN.

A can of this substance labeled “Transatlantic ratin” was furnished by the American agents representing the Bacteriological Laboratory, Copenhagen, Denmark. The can bore the date January 26, 1909, and was stated to be “effective for six months from date of production.”

On April 13, 1909, this sample was given to Passed Asst. Surg. W. H. Frost for examination, and he obtained the following results:

April 13, 1909: Can of ratin opened with aseptic precautions. Contents mixed with about equal bulk of clean fresh lard.

A portion of this about equal to one tablespoonful fed to each of six white rats previously deprived of food for twenty-four hours. All the rats ate some of the bait at once. Feeding at 2 p. m.

April 14: Five rats very sick, having convulsions; partially paralyzed. One dead.

April 15: Three more rats found dead. Remaining 2 recovering.

The pathological change in all the above cases consisted chiefly of intense congestion of intestines, both large and small.

Cultures from the original case of ratin, on agar, bouillon, and in fermentation tubes, negative except staphylococcus in one tube.

Cultures taken from heart’s blood and other organs of the 4 dead rats all negative, except in one case a growth of a staphylococcus resembling S. pyogenes citreus.

April 20: Two rats fed on half agar slant culture of the staphylococcus obtained from heart’s blood of rat No. 1. Result of feeding negative after several weeks.

NOTE. The absence of a colon-like organism in this virus and the rapid death of the animals with convulsions suggested a chemical poison, which it is believed this can contained.—M. J. R.

EXPERIMENTS WITH MICRO-ORGANISMS FOR DESTROYING RATS, CONDUCTED BY THE UNITED STATES BIOLOGICAL SURVEY.

Footnote AV:

This report was furnished by Dr. A. Hart Merriam, Director of the Biological Survey.

RATIN.

The Biological Survey, Department of Agriculture, in cooperation with the Bureau of Animal Industry, has experimented with “ratin.” The material (ratin No. 2—labeled “Transatlantic ratin”) was furnished by the American agents in New York. Although the agent claimed that this was a bacterial preparation and that “it would kill for six generations,” it proved to be a glucoside poison (probably squills) and contained no bacteria of any kind. A number of experiments were made with it, and it proved to be an effective rat poison. In some instances the animals died within two hours after eating it, and in two experiments all the animals fed died within twelve hours. In other experiments, however, a considerable percentage of the affected rats recovered, and subsequent attempts to kill them with ratin No. 2 failed. Some were immune to its effects and others too wise to eat it a second time. More than a hundred rats were used in the experiments; but the main object—to test the communicability of the disease caused by ratin bacteria in healthy rats—failed, of course, since, as above stated, the preparation experimented with contained no bacteria, but was merely a vegetable poison. Before its character was fully determined, 15 rats killed in the experiments were eaten by 5 healthy rats; the latter were unaffected.

It should be noted that the labels on the tins containing transatlantic ratin were misleading. The user was warned to open the packages in dim light and to allow no moisture to come in contact with the contents, as the bacteria were very sensitive to light and moisture. The contents of the can were to be used at once. As a matter of fact the contents of one can were exposed to severe drying in heat and sunlight for four days and then soaked in water for two days. Afterwards the preparation was fed to different rats for a further period of four days, and its virulence was retained to the last.

The transatlantic ratin is in a solid medium, apparently bread and molasses. Its keeping qualities are excellent, and it is an effective poison for rats, but far too expensive for extensive use. A can costing $1.50 is enough for only 15 baits.

Its harmfulness to domestic animals was not fully tested. Dogs and cats refused to eat it and vomited it when it was forced upon them. Several animals, including a dog, were killed by injections of the poison in concentrated form.

A shipment of ratin No. 1 (the solid bacterial ratin, said to retain its virulence for two months) was received June 4, 1909. This preparation was dated May 8 and should have been still virulent. The contents of a can mixed with milk was fed to 8 adult rats on June 7. All of the baits were eaten, but no result followed. Cultures of the bacteria showed strong growths of new colonies.

On July 6 the contents of another can were fed to 1 adult and 16 young rats. One of the young was found dead on the morning of July 14. Cultures were made from the dead rat, but the bacillus was not recovered. Up to July 28 none of the other rats have been affected.

AZOA.

Several trials of azoa for the destruction of rats have come under the observation of members of the Biological Survey. Experiments made in the building occupied by the Interstate Commerce Commission were at first promising, but from a second invoice of the virus no results were obtained. In the buildings of the National Zoological Park 72 bottles of azoa were used, but the results were for the most part negative. In a store in south Washington where this preparation had been used the stench of dead rats was very strong, showing a measure of success.

DANYSZ BACILLUS.

Some three years ago the Biological Survey, assisted by the Bureau of Animal Industry, tested the efficiency of Danysz virus. In the laboratory from 10 to 50 per cent of rats fed on the virus died. In the field, however, results obtained were unsatisfactory. Only 1 dead rat was found from which the bacillus was recovered. Experiments with field mice gave better results. All the mice fed in confinement died, and field experiments resulted in many dead mice from which the bacillus was recovered.

EXPERIMENTS DURING THE SAN FRANCISCO PLAGUE OUTBREAK.

Footnote AW:

These experiments were made by Passed Asst. Surg. G. W. McCoy, United States Public Health and Marine-Hospital Service, in 1907–8 during the plague campaign in San Francisco and here published for the first time.

Several proprietary biological products sold as rat exterminators were made the subject of seven experiments on wild San Francisco rats, for the purpose of ascertaining whether they were efficient for the purpose for which they were sold. Seventy-six rats were used in these experiments. About 10 per cent died within a month and there was considerable doubt as to whether all of the deaths that occurred were due to the agent used.

The following is a brief statement of the work done with these agents. In each case the rats used were wild Mus norvegicus, caught in San Francisco.

RATIN NO. 1.

Made by the Bakteriologik Laboratorium, Copenhagen, marked: “Effective two months from April 28, 1908.” The preparation comes ready for use in the form of a moist, mealy mass. On May 28, about 6 ounces of the material was fed to 12 rats. They all remained well until thirty days after feeding them when the experiment was regarded as terminated.

DANYSZ VIRUS.

The Danysz Virus Company (Limited), of London, furnished a preparation in the form of a culture on a slant of solid medium, said to be gelatine. The tube was marked: “To be used before June 1, 1908.” The contents of the tube, mixed with bread, according to directions, was fed to 6 rats. On the twenty-first day but 4 rats remained, 2 having died and been devoured by their companions. The 4 that remained were chloroformed, as the cage was needed for other purposes. Post-mortem examination showed them to be entirely normal.

RATITE.

Furnished by the Pasteur Vaccine Company, Chicago. This preparation is in the form of a culture in a liquid medium, presumably broth. The bottle was dated April 10, 1908, and the label stated that it should be used within twenty days from date of preparation. On April 29, 1908, 9 rats were fed with about 6 ounces of the preparation, mixed according to directions. The rats all remained alive and well, and when chloroformed on June 1, 1908, presented no abnormality on post-mortem examination. In another experiment the contents of a bottle of ratite was fed to 6 medium-sized Mus norvegicus. None of the animals died from the effects of the agent, and when they were killed on the fifty-fifth day after the feeding were found to present no lesions.

The remaining work was done with rat virus, sometimes called “Mouratus.” It is made by the same concern that makes the ratite. The rat virus comes in the form of a culture on a solid medium. The contents of three tubes was fed to 6 rats on May 26, 1908. Three of these rats died within thirty days. Only one was secured for examination before it had been mutilated beyond the possibility of making a satisfactory examination. This rat had a large yellow liver and a very large, dark, firm spleen. These appearances were probably due to the agent used and it is not unlikely that these 3 rats died from its effect. It will be observed that a very large dose was given. On another occasion four tubes of Mouratus were used for feeding 6 Mus norvegicus. One of the rats died on the fifteenth day, showing at autopsy an enlarged granular spleen and a granular liver. The other rats were alive and well at the end of thirty-four days when the experiment was discontinued.

Subcultures on broth were made from this preparation on three occasions, always well within the time limit on the label. The cultures were incubated in the dark, at room temperature, for forty hours on each occasion. Liberal amounts of the subculture were fed to a total of 31 rats. At the end of thirty days, it was found that only 2 of these rats had died. The others were alive and apparently well.

One objection to these agents which I have not seen stated is the following: The lesions caused by at least some of these members of the paracolon group may readily be mistaken for the lesions of plague, or it will perhaps be more accurate to say they give rise to lesions that create in one’s mind a suspicion of plague infection, and I have had to put many a rat to the guinea-pig test in order to make certain that a Danysz infection was not associated with the infection of plague, or that a Danysz rat was not a plague rat. Of course, this is of no consequence except in a community where antiplague measures are being taken, and an observer of limited experience who did not put a rat to a pretty rigid test would probably call some plague infected when in reality such is not the case.

In addition to the data set forth in this report, I have on several occasions fed the tissue of rats dead of Danysz infection to other rats, but have never succeeded in reproducing the disease. In other words, I have had no success whatever in raising the virulence by passage through animals.

OPINIONS OF OTHERS.

Kitasato, 1906, states that the typhoid bacillus of the rat, which has been effectively used for killing field mice, has been found useless for house rats (Mus rattus) and therefore they no longer employ it.

Footnote AX:

Kitasato, S.: Combating plague in Japan. Philippine Journ. Sci., vol. 1, 1906, p. 465.

Melvin, 1908, reports that recently several new rat viruses were investigated in the Bureau of Animal Industry, with the result that the experiments clearly demonstrated the ineffectiveness and unreliability of the preparations tested.

Footnote AY:

Melvin, A. D.: Report of the Chief of the Bureau of Animal Industry for 1908. Washington, 1908.

Räbiger and Schwinning, 1906, tested the culture discovered by G. Neumann and prepared by the joint stock company “Ratin” at Copenhagen by applying it to rat destruction. Of house rats 90 per cent died; black rats 42.9 per cent; while horses, dogs, goats, sheep, fowls, and pigeons suffered no harm. Of seven experiments practically carried out, six showed very good results; in one favorable results were absent, which agrees with the experiments made in Denmark. There it was likewise found that in individual locally limited places the rats were able absolutely to withstand the infection of ratin.

Footnote AZ:

Räbiger and Schwinning: Versuche mit Ratin, einem neuen Ratten tötenden Bacillus. Mitth. d. deutsch. Landw.-Gesellsch., 1906, No. 18. Rev. by Ehrenberg in Centblt. f. Bakt., 2. Abt., vol. 18, 1907, p. 375.

Räbiger, 1905, states that experiments with Loeffler’s mouse typhus bacillus and the bacillus of Danysz virus have been carried to the conclusion that these bacterial preparations must be characterized as practically worthless.

Footnote BA:

Räbiger, H.: Ueber Versuche zur Vertilgung der Ratten durch Bakterien. Landw. Woch. f. d. Prov. Sach., 1905, p. 142. Rev. by Stift in Centblt. f. Eakt., 2 Abt., vol. 15, 1905, p. 86.

In 1903 Neumann discovered in Denmark a rat-killing bacillus, which has been placed on the market by a society under scientific control under the name of “ratin.” Feeding experiments with this bacillus were tried under conditions as nearly natural as possible upon white mice, gray house mice, long-tailed field mice, and gray rats. The experiment animals were fed with cubes of white bread impregnated with virulent cultures. White mice show the least power of resistance, since they die within six days; house mice died in six to nine days; the greater part of the rats died from the sixth to the sixteenth day after feeding; a small percentage lived. The long-tailed field mice, which are shown to be insusceptible to Loeffler’s bacillus, also remained perfectly healthy after repeated feedings with bread infected with ratin.

Brooks, 1908, reports the results of tests made with azoa on rats and mice, both in captivity and at large, but without any apparent discomfort to the animals. One of the tests is described as follows:

Footnote BB:

Brooks, Fred E.: Notes on the habits of mice, moles, and shrews. A preliminary report. Bull. 113, W. Va. Univ. Agric. Exper. Sta., Morgantown, W. Va., Jan., 1908.

A supply of the azoa was obtained direct from the laboratories of the manufacturers. On July 27, 1907, while the material was yet fresh, three young Norway rats were caught and kept confined in a large wire rat trap. Beginning with the date given, and for a period of forty days thereafter, azoa was fed to the rats at intervals of a few days until ten 75-cent bottles had been consumed. The rats ate the cracked grain with which the virus was mixed very readily, and other food was denied them each time the azoa was given until every particle was eaten. At the end of the forty days the rats were still apparently in a healthy condition, and were removed from the trap and killed with a club.

Thompson, 1906, states that three laboratory attempts have been made to destroy rats with imported strains of Danysz rat virus without success. Danysz having arrived at Sydney to study a similar method of destroying rabbits, the opportunity was taken of making a further attempt under his supervision with virus which had been imported and subsequently increased to the requisite degree of virulence, and had been placed at Thompson’s disposition. The grounds of the Gladesville Asylum, a large institute for the insane, were chosen for the tests, which were conducted by Dr. R. J. Millard.

Footnote BC:

Thompson, J. Ashburton: Report of the Board of Health on plague in New South Wales, 1906. On a sixth outbreak of plague at Sydney, 1906. Legislative assembly, N. S. W., 1907.

Millard summarized his result by stating that they can not be considered a satisfactory demonstration of the efficacy claimed for the Danysz virus. The results indicate a rapid loss of virulence, which must be obviated if this virus is to be of utility for rat destruction.

Again, in 1907, during the seventh outbreak of plague in Sydney, Thompson had Millard test the preparations known as azoa and ratin. The laboratory results with these preparations were similar to those made by other investigators. Experiments made upon the ship Hartfield with azoa produced no considerable epizootic. The fatality among such rats as were infected was small. The practical tests with azoa upon several areas along the harbor front also resulted in disappointment.

Footnote BD:

Thompson, J. Ashburton: Report of the board of health on plague in New South Wales, 1907. On a seventh outbreak of plague at Sydney, 1907. Legislative Assembly, N. S. W., 1908.

The tests made with ratin upon the bark Quilpe produced no epizootic among the rats, and of the rats caught none of them showed infection; and the field experiment at Gladesville also resulted negatively so far as dead or sick rats were concerned. Nevertheless, there was apparently considerable diminution in the rat population of this area.

Foster, 1908, reports unfavorably upon the results of tests made of some of these rat viruses. Laboratories were opened for the use of different parties who wished to make tests. The tests were conducted under their own supervision. The rats which were not fed on anything but grain died as freely as those that had been fed on azoa. So far as this preparation is concerned Foster states that it is absolutely useless to depend upon it.

Footnote BE:

Foster, N. K.: The danger of a general plague infection in the United States. Proc. Confer. State and Prov. Boards of Health of N. America, 1908, p. 15.

Several reports are found in print in which the rat virus was laid out in certain localities and shortly afterwards the rats disappeared—at least no more were noticed. Such observations are apt to be misleading, for rats are migratory. They come and go, especially when disturbed. Further, it is doubtful, as far as plague is concerned, whether it is desirable to drive the rats away, for they may thus scatter the infection.

S. S. Mereshkowsky and E. Sarin have recently studied ratin II, put out by a Copenhagen firm—“Bakteriologisches Laboratorium Ratin.” The label upon the can of ratin II states that it is a bacterial culture, which produces in rats an infectious and fatal disease, killing them in two to eight days. The samples used by the authors were obtained as needed from the St. Petersburg representative of the firm. Feeding experiments carried out with gray rats (Mus decumanus) showed that the rapidity and severity of the symptoms was proportional to the amount ingested. No positive results were obtained from the bacteriological examination of the bodies.

Footnote BF:

Ueber das Ratin II. Centralb. für Bakt. Parstk. u. Infectsk. Originale. Bd. 51. Heft 1. July 17, 1909, p. 6.

The ratin itself was sometimes found to be sterile, sometimes found to contain several varieties of bacteria and fungi, but no one variety was constantly present.

The potency of the ratin was not altered by exposure to 100° C. for one hour or 120° C. for five minutes. It was destroyed, however, by burning to an ash.

Identical poisonous results were obtained upon rats by feeding them with “Scilla maritina cum bulbo rubro.”

Microscopical examination disclosed a small portion of a lamella, identified as belonging to the Liliaciæ, to which family squill belongs.

The authors conclude that ratin II is not a bacterial culture, but a poison rendered more dangerous to persons and domestic animals by the misleading statements of its makers.

PATHOGENICITY FOR MAN.

Loeffler rather took it for granted at first that his Bacillus typhi murium was harmless for man. In order to remove the fears of the peasants in his campaign against the field mice in Thessaly he fed pieces of bread impregnated with the cultures to chickens, pigeons, dogs, hogs, horses, asses, sheep, and goats. No ill effects resulted. Further, some of the men who were distributing the prepared virus ate pieces of the infected bread in the presence of all and, it appears, suffered no ill effects.

Footnote BG:

Loeffler, F.: Die Feldmausplage in Thessalien und ihre erfolgreiche Bekämpfung mittels des Bacillus typhi murium. Centblt. f. Bakt., vol. 12, 1892, p. 1.

Up to this time Loeffler had made no human experiments, but thought it improbable that his bacillus was harmful to man. He considered this view confirmed by the fact that he and his companions and still more so the peasants, handled large quantities of the virus without thorough disinfection of their hands and suffered no untoward effects.

Since that time, however, several mishaps have occurred. Instances of serious sickness and even death have been attributed to infection with the bacterial virus used for the destruction of rats.

Further, there is practically no difference between the Bacillus typhi murium and the para-typhoid bacillus which is the well-known cause of meat poisoning, and the Bacillus enteridion of Jarbues, which is associated with intestinal disorders.

It is true that persons have purposely partaken of the rat virus to prove that it is harmless to man; but it must be remembered that persons have partaken of cultures of cholera, typhoid, and other bacteria without apparent injury to themselves. The flora and condition of the gastro-intestinal tract, the amount and virulence of the infection, and other conditions (“Y” and “Z” of Pettenkofer) play an important rôle in the production of these diseases.

The following references from the literature give the instances in which the B. typhi murium, or similar rat viruses, have been held responsible for the disease in man:

Trommsdorff carefully studied 13 suspected cases near Munich in early May, 1903. Nine of these came into direct contact with the virus, three ate and associated with these, and the remaining one only smelled of the virus. One died from vomiting and severe diarrhea. The illness, which set in usually two days after contact with the virus, was for the most part simple diarrhea of two to seven days’ duration (two to eight stools daily); in only three or four cases was there vomiting. The one fatal case seemed due to a confusing chain of circumstances, gross dietetic and alcoholic excesses in a weak, emaciated, presumably phthisical man whose three brothers had died of phthisis. One man, case No. 2 in the table, known to have eaten three pieces of infected bread, suffered only with a mild diarrhea.

Footnote BH:

Trommsdorff, R.: Ueber Pathogenität des Löfflerschen Mäustyphusbazillus beim Menschen. Münch. med. Woch., vol. 50, 1903, p. 2092.

In all cases errors of diet could be proven, and diarrhea was not uncommon at that season. The same physician attended during this period ten other cases of similar diarrhea in the vicinity having nothing to do with rat virus. The stools, however, did not have the same pathogenicity for mice, guinea pigs, or rabbits.

Trommsdorff specially points out the fact that the bacillus of mouse typhoid can multiply vigorously in the human intestine. It demands greater caution in the application of the cultures and more careful supervision over their use.

Finally, attention is invited to the fact that, contrary to the usual custom, the cultures of rat virus here used had been grown on milk, which might account for the increased virulence.

The following table gives a brief summary of ten cases with the results of the agglutination tests:

Agglutination tests with serum of recovered cases, May 17, 1908. ──────┬─────────────────────────┬────────┬───────────────────────────── Case. │ How infected; symptoms. │Strains.│ Serum dilutions. „ │„ │„ │¹⁄₂₀ │¹⁄₄₀ │¹⁄₆₀ │¹⁄₁₀₀│¹⁄₂₀₀ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼───── 1 B. │(From this case stool 2.)│A │ + │ + │ + │ ± │ 0 K. │ Laid rat poison │ │ │ │ │ │ │ 5–2,5–5; some days │ │ │ │ │ │ │ later diarrhea; later │ │ │ │ │ │ │ vomiting; convalescence│ │ │ │ │ │ │ and recovery May 10. │ │ │ │ │ │ „ │„ │B │ + │ + │ + │ ± │ 0 „ │„ │C │ + │ + │ + │ ± │ 0 „ │„ │D │ + │ + │ + │ + │ ± ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼───── 2 K. │Ate three pieces of │A │ + │ 0 │ 0 │ 0 │ 0 E. │ infected bread May 2; │ │ │ │ │ │ │ mild diarrhea several │ │ │ │ │ │ │ days. │ │ │ │ │ │ „ │„ │B │ + │ ± │ 0 │ 0 │ 0 „ │„ │C │ 0 │ 0 │ 0 │ 0 │ 0 „ │„ │D │ + │ ± │ 0 │ 0 │ 0 ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼───── 3 H. │Brought the virus April │A │ + │ 0 │ │ │ B. │ 28; perhaps touched it;│ │ │ │ │ │ │ next day diarrhea and │ │ │ │ │ │ │ vomiting; recovery │ │ │ │ │ │ │ after several days. │ │ │ │ │ │ „ │„ │B │ + │ 0 │ │ │ „ │„ │C │ + │ 0 │ │ │ „ │„ │D │ − │ − │ − │ − │ − ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼───── 4 G. │Father of man that died; │A │ + │ + │ + │ + │ 0 S. │ laid virus; two days │ │ │ │ │ │ │ later mild diarrhea for│ │ │ │ │ │ │ one or two days. │ │ │ │ │ │ „ │„ │B │ + │ + │ + │ + │ 0 „ │„ │C │ + │ + │ + │ 0 │ 0 „ │„ │D │ + │ + │ + │ + │ ± ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼───── 5 J. │On April 27 laid virus; 2│A │ ± │ 0 │ 0 │ 0 │ 0 K. │ days later diarrhea for│ │ │ │ │ │ │ several days. │ │ │ │ │ │ „ │„ │B │ ± │ 0 │ 0 │ 0 │ 0 „ │„ │C │ ± │ 0 │ 0 │ 0 │ 0 „ │„ │D │ − │ 0 │ 0 │ 0 │ 0 ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼───── 6 J. │Laid virus April 27; two │A │ 0 │ 0 │ 0 │ 0 │ N. │ days later had diarrhea│ │ │ │ │ │ │ for several days. │ │ │ │ │ │ „ │„ │B │ + │ + │ + │ ± │ „ │„ │C │ 0 │ 0 │ 0 │ 0 │ „ │„ │D │ + │ + │ + │ ± │ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼───── 7 G. │“Held” the virus April │A │ + │ + │ + │ + │ ± I. │ 28. Next day diarrhea │ │ │ │ │ │ │ for four days. │ │ │ │ │ │ „ │„ │B │ + │ + │ + │ + │ ± „ │„ │C │ + │ + │ + │ + │ ± „ │„ │D │ − │ − │ − │ − │ − ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼───── 8 H. │Ate and associated with │A │ + │ + │ 0 │ │ R. │ persons who handled │ │ │ │ │ │ │ virus; diarrhea several│ │ │ │ │ │ │ days. │ │ │ │ │ │ „ │„ │B │ + │ − │ 0 │ │ „ │„ │C │ + │ ± │ 0 │ │ „ │„ │D │ − │ − │ − │ │ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼───── 9 K. │Associations as case 8; │A │ + │ + │ + │ + │ S. │ headache several days │ │ │ │ │ │ │ and loss of appetite. │ │ │ │ │ │ „ │„ │B │ + │ + │ + │ + │ „ │„ │C │ + │ ± │ 0 │ │ „ │„ │D │ − │ − │ − │ − │ − ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼───── 10 │Associations as case 8; │A │ 0 │ 0 │ 0 │ 0 │ │ diarrhea for eight │ │ │ │ │ │ │ days; vomiting several │ │ │ │ │ │ │ days. │ │ │ │ │ │ „ │„ │B │ + │ + │ + │ ± │ „ │„ │C │ 0 │ 0 │ 0 │ 0 │ „ │„ │D │ + │ + │ + │ ± │ ──────┴─────────────────────────┴────────┴─────┴─────┴─────┴─────┴───── A = Strain from Loeffler. B = Strain from market virus. C = Strain from stool 1 (fatal case). D = Strain from stool 2 (case 1 of table). − = No test made. 0 = Negative. ± = Slight. Controls = Serum of five normal persons tested as above; gave in no case agglutination higher than 1 : 20.

The attending physician, noting that most of his patients had come into recent contact with rat virus (B. typhi murium) and suspecting that to be responsible, sent specimens of stools to the Hygienic Institute at Munich, where they were carefully examined with reference to this subject.

Organisms identical with Loeffler’s B. typhi murium were isolated from the two stools examined and these cultures were compared with and conformed with a culture of B. typhi murium obtained from Loeffler and also a culture from the virus on the local market.

Two guinea pigs injected with cultures from the two stools gave, after the second injection, serum which agglutinated all the above organisms 1:200. A mouse typhoid serum obtained from Loeffler agglutinated all the above strains distinctly in dilutions 1:640 and slightly in 1:1280.

In conclusion, the author considers three possibilities: 1. The mouse typhoid bacillus was the cause of the illness. 2. The bacillus was accidentally present, having no part in the production of the symptoms. 3. The bacillus was able to multiply only in case pre-existing intestinal trouble; then, however, causing the inflammation.

The case of Mayer, who became infected during the course of some laboratory experiments, is particularly instructive.

During an epidemic of mouse typhoid among his laboratory mice, evidently spread from some inoculated mice by ants, Mayer who had personally handled the infected mice and their cages, became sick July 15, just seven days after the first appearance of the ants and after the observed rise in virulence of the mouse typhoid among the mice. His clinical history is as follows:

Footnote BI:

Mayer, Georg: Ueber die Verschleppung typhöser Krankheiten durch Ameisen und die Pathogenität des Loeffler’schen Mäusetyphusbazillus für den Menschen. Münch. med. Woch., vol. 52, 1905, p. 2261.

July 15: Weakness, epigastric pain, obstipation, temperature 37.7, pulse 90.

July 16: Slight diarrhea, increase of pain in region of trans-colon, temperature 38.3, pulse 98.

July 17: Diarrhea continued, pains increased—severe, chill in evening, temperature 39.1, pulse 102.

July 18: Obstipation, symptoms worse, chill again in evening, temperature 39.4, pulse 104.

July 19: Symptoms better, stools from purgative, evening temperature 36.9, pulse 68.

July 20: Left bed. Temperature and pulse normal, but weakness and slight epigastric pains continued till August 7.

Patient’s serum agglutinated as follows:

──────────────────────────┬──────────────┬──────────────┬────────────── │ Typhoid. │ Paratyphoid. │Mouse-typhoid. ──────────────────────────┼──────────────┼──────────────┼────────────── July 23 │ 1–50+│ 1–50+│ 1–250+ August 7 │ 1–50+│ 1–50+│ 1–100+ August 16 │ 1–50+│ 1–50+│ 1–50 + ──────────────────────────┴──────────────┴──────────────┴──────────────

Footnote BJ:

Slight

The bacillus of mouse typhoid was isolated from the patient’s stools July 21 and 23. Negative results thereafter. Examinations continued a month.

Same organism isolated from urine July 21. Negative thereafter.

The author concludes that the B. typhi murium is able to cause in man a rather severe acute illness of short duration.

Shibayama gives the following report of outbreaks of human infection that have come to his knowledge in Japan, where mouse-typhoid virus has been used in considerable quantities.

Footnote BK:

Shibayama, G.: Ueber Pathogenität der Mäusetyphusbazillen für den Menschen. Münch. med. Woch., May, 1907, p. 979.

Outbreak 1. In April, 1905, in a village of the Province of Saitama, 30 people became ill and 2 died with severe gastro-intestinal symptoms. Outbreak investigated by Dr. H. Sezuki, district medical officer, formerly of the Tokio Institute for Infectious Diseases.

It was found that all the 30 people had partaken of a dish of cooked vegetables served at a meeting of the town council, and that for application of sauce to these vegetables (after cooking) a wooden vessel had been used which two days before had been used for mixing mouse-typhoid virus with meal, without subsequent cleansing or sterilization.

The symptoms came on within twelve to forty-eight hours thereafter (usually twenty hours), chill or chilly sensations, rise of temperature to 38° or 39° C., or even to 40° C.; face flushed; pulse accelerated; great weakness; thirst, nausea, colicky pains in abdomen followed by severe diarrhea and vomiting. In general, the fever and diarrhea lasted two or three days; but malaise, anorexia, weakness, and mucous stools persisted for several days. The more severe cases showed choleraic symptoms of collapse. Two persons died in spite of medical treatment—a 6-year old boy and a man of 43, on the second and third day, respectively.

From the intestinal contents of these two cases, from the stools of several other cases, and from the remnants of the dish of vegetables in the wooden bowl an organism was isolated, which was demonstrated to be identical with the bacillus of mouse typhoid.

These results were confirmed at the Tokio Institute for Infectious Diseases by Shibayama, by biological and immunizing tests.

Outbreak 2. On December 7, 1905, a peasant of a village in the Province of Miyaki brought home some mouse virus mixed with meal in cakes. This being mistaken for “mochi” was eaten about 2 p. m. the next day by two little girls, 3 and 8 years old, respectively, and their grandfather, 61 years old.

The man and the 8-year-old girl became sick at 9 p. m. the same day and the other child at about 3 p. m. on December 9. The symptoms in all cases were those of severe gastro-enteritis, as described under outbreak 1.

The man died December 12, the 8-year-old child died on the 10th; the 3-year-old child recovered after several days’ illness. These three alone ate of the virus and no other persons in the house became sick.

No bacteriological examination was practicable.

Outbreak 3.—In a village of the Province of Iskawa, on April 22, 1906, a lot of rat poison was prepared by mixing agar cultures of the mouse-typhoid bacillus with meal and water in a large wooden bowl.

On April 24 there was a festival in the village at which about 170 persons were served with 240 pounds of rice, which, after being cooked, was kneaded into cakes in a wooden bowl. About 80 pounds of this rice was so kneaded in the bowl previously used for preparing the rat poison. Twenty to twenty-four hours later 120 people who had eaten of the rice became ill with the already described symptoms of gastro-enteritis, of mild type among the strong but severe among the children and old people. Eighty-nine cases came under medical treatment. There were no deaths, but a number of cases were confined to bed for a week or more; mild cases recovered in one to three days.

No bacteriological examination was made, but the physicians and town officials were unanimously of the opinion that the rat virus was the cause of the outbreak.

Outbreak 4.—A peasant of the province of Niigata brought home on May 14, 1906, some rat virus (cultures of mouse-typhoid bacilli mixed with meal) which he laid away. Two of his grandchildren—a boy of 5 and a girl of 7—together with the 4-year-old daughter of a neighbor, found and ate the rat virus. The next day all three children became ill with severe gastro-enteritis, of which the 4-year-old child died on the third day. The others recovered after several days of medical treatment.

Outbreak 5.—On May 16, 1906, a peasant in the province of Jamagata brought home some rat virus (6 c. c. cultures of mouse-typhoid bacillus mixed with meal), which was accidentally mixed with the feed given to a healthy horse next morning. The same evening the horse showed loss of appetite and appearance of sickness. Within two days he developed a severe enteritis, of which he died on the seventh day. The body was buried, but was dug up in the night by a laborer who cut off the hind quarters, took them home, and distributed the meat among friends and neighbors.

Within three days 34 persons who had eaten of this meat became ill with symptoms of severe gastro-enteritis. A 72-year-old man died after five days; the others recovered in three to eleven days.

This outbreak was investigated by Dr. H. Segawa, a medical officer of the province and former member of the institute at Tokyo, who isolated from the remains of the horseflesh by plate cultures and animal inoculations, an organism identical with the bacillus of mouse typhoid. A culture was sent to Shibayama, who carefully verified it (details not given).

Shibayama concludes: In all cases the close relationship between the bacillus of mouse typhoid and the illness was established; and he thinks this organism must be accepted as the direct cause of the outbreaks.

Referring to Loeffler’s uniformly negative human experiments, he calls attention to known cases where men have taken virulent cultures of typhoid, diphtheria, etc., without infection. According to many bacteriological investigations, B. typhi murium is identical with the bacillus of enteritis. If it is proven that the latter is a cause of acute gastro-enteritis then the conclusion is likewise justified that the B. typhi murium is frequently pathogenic for man, causing an acute gastro-enteritis.

Fleischanderl a reports six cases of illness—three severe and three mild—occurring in his practice in the latter part of April, 1908, presenting the following symptoms: Onset with rapidly increasing body pains, followed in a few hours by diarrhea, rise of temperature, and general prostration; in the next two or three days aggravation of the symptoms, fever (39° to 40° C.), copious diarrhea, vomiting (in one case), severe body pains, vertigo, and considerable prostration. Symptoms abated quickly in a few days, leaving considerable prostration, convalescence requiring two weeks in one case. In the less severe cases there was no fever, and the other symptoms were generally milder.

Footnote BL:

Fleischanderl, Fritz: Mitteilung über einige Krankheitsfälle, hervorgerufen durch Mäustyphusbazillen. Munch. med. Woch., vol. 56, Feb., 1909, p. 392.

The simultaneous appearance of these and other similar rumored mild cases among the neighbors (about 20 in all) pointed to a common cause. It was found that three of the six cases were in people who had handled mouse-typhoid cultures the day before their illness, taking no precautions to avoid infection.

The other three occurred in a family which, on the day before the onset of the illness, had drunk raw milk obtained from a house where the rat virus had been used shortly before, and only three members of the family who drank the milk became ill.

In order to prove the etiology of these cases Fleischanderl, who had never suffered any intestinal troubles, had had nothing to do with any case of typhoid fever for a year, and was in excellent health, took a culture of the mouse-typhoid bacillus as used in the neighborhood, rubbed a glass rod over the surface, washed it off in a glass of water, and drank this before breakfast on the morning of May 3.

In twenty-two hours he experienced mild, increasing body pains, followed within a few hours by diarrhea, and a few hours later by slight chill, rise of temperature to 38.2, pulse 106, severe pains in body, and feeling of great weakness.

May 4, 9 p. m.: Temperature 39.2° C., pulse 120. Height of symptoms.

May 5: Temperature 38.2° to 38.5° C., pulse 106 to 120. Other symptoms continued.

May 6: Temperature and pulse normal. All symptoms disappeared except weakness, which lasted two days.

Bacteriological investigations conducted by Herbert Berger in the K. K. Serotherapeutischen Institut and by Doctor Reichel, assistant in the Hygienic Institute of the University of Vienna, follow:

From the stools of one of the patients infected from milk an organism was isolated which, injected into mice (1 c. c. emulsion of forty-eight-hour culture), killed them in two to five hours. Mice infected by eating these dead mice died in thirty to forty-eight hours.

Control mice inoculated similarly with a culture of the market mouse-typhoid virus died in twenty to thirty hours, while the mice infected through eating these died after three to four days.

The following strains were used for cultural agglutination tests:

A. From stools of patient infected from milk.

B1. Market virus used in injecting mice.

B2. Market virus taken by author.

C25. From stools of author twenty-five hours after infection.

C55. From stools of author fifty-five hours after infection.

LL. Stock culture of Loeffler’s mouse-typhoid bacillus.

LP. Stock culture of para-typhoid bacillus.

All organisms (A-C55) were demonstrated as motile bacilli, not liquefying gelatine, not forming lactic acid, and forming gas from dextrose.

The serum of a rabbit after two injections of LL agglutinated LL and LP in dilution of 1:1280, did not agglutinate A, B1, B2, C25, and C55.

Serum of rabbit after one injection of B2 agglutinated in 1:320 dilution A, B1, B2, C25, C55, and LL; did not agglutinate LP.

Serum of rabbit after one injection of C25 gave exactly similar results.

Doctor Reichel considers it proven that the organisms A to C55 are undoubtedly identical with Loeffler’s bacillus of mouse typhoid, and distinct from para-typhoid bacilli. The author considers it proven that this bacillus was the sole cause of the cases of enteritis observed.

Recently Mallory and Ordway, in a paper read before the American Association of Pathologists and Bacteriologists held in Boston, reported that lesions analogous to the early stages of typhoid lesions may be produced in rats by the use of Danysz virus.

Footnote BM:

Mallory, F. B., & Ordway, T.: Lesions produced in the rat by a typhoid-like organism (Danysz virus). Journ. Am. med. assn., vol. 52, May 1, 1909, p. 1455.

In view of these facts the statements of some of the advertising matter of certain rat viruses call for revision.

REFERENCES TO THE LITERATURE.

Loeffler, 1889, gives an account of two spontaneous outbreaks among the mice kept at the Hygienic Institute at Griefswald. It was from these animals that he obtained and described the original B. typhi murium. He determined that the infection was by ingestion and that the organism was especially virulent for field mice. He described the organism in detail and also the lesions.

Footnote BN:

Loeffler, F.: Ueber Epidemieen unter den im hygienischen Institute zu Griefswald gehalten Mäusen und über die Bekämpfung der Feldmäusplage. Centblt. f. Bakt., Orig., vol. 11, 1898, p. 129.

Laser, 1892, reports that on the morning of February 6, 1892, 70 of the 76 field mice (Mus agrarius) used as experiment animals in the Hygienic Institut at Königsberg were found dead. A small bacillus twice as long as broad, displaying a very lively specific motility, was isolated from the spleen. It was tested upon animals and all the results compared with Eisenberg’s tables and found to be closely allied to the bacillus of ferret plague (Ebert-Schummelbusch), to the bacillus of American swine plague (Billings), and to that of French swine plague (Chantamesse and Cornil).

Footnote BO:

Laser, Hugo: Ein neuer für Versuchsthiere pathogener Bacillus aus der Gruppe der Frettschen-Schweinseuche. Centblt. f. Bakt., Orig., vol. 11, 1892, p. 184.

Mereshkowsky, 1893, isolated an organism at the Royal Bacteriological Institute at St. Petersburg from a stock of Zisel (Spermophilus musicus) among which a spontaneous epizootic had occurred. The author found this culture to be virulent for domestic and field mice.

Footnote BP:

Mereshkowsky, S. S.: Ein aus Zieselmäusen ausgeschiedener und zur Vertilgung von Feld-resp. Mäusen, geeigneter Bacillus. Centblt. f. Bakt., Orig., vol. 17, 1895, p. 742.

Zupnik, 1897, states that Joseph, of the Agricultural Institute of Breslau, in 1882 originated the use of favus fungus for the destruction of mice. Zupnik tested B. typhi murium and Danysz virus upon mice. No experiments with rats.

Footnote BQ:

Zupnik, Leo: Ueber die pratische Verwendbarkeit der Mäuse bacillen inbesondere des Loeffler’schen Bacillus typhi murium. Centblt. f. Bakt., Orig., vol. 21, 1897, p. 446.

Issatschenko, in 1898, described briefly a bacillus obtained by him from gray rats. Recent investigation showed this bacillus to be very virulent for rats and mice, but harmless for the different species of domestic animals. Four hundred and forty-three experiments were made upon rats with pure cultures of the bacillus combined with dough and fed to the rats. He gives a table showing that the mortality occurred in 431 rats at an average of ten and one-half days. The greatest mortality occurred during the first fifteen days (84.2 per cent), with the greatest number on the seventh day (20.1 per cent).

Footnote BR:

Issatschenko, B.: Untersuchungen mit dem für Ratten pathogenen Bacillus. Centblt. f. Bakt., Orig., vol. 31, 1902, p. 26.

Danysz, 1900, isolated a cocco-bacillus during an outbreak of spontaneous disease amongst field mice which presented the general characteristics of the colon bacillus and to this extent resembled Loeffler’s bacillus (B. typhi murium), and which from the beginning exhibited some pathogenicity for gray rats (M. decumanus). Of ten such rats fed upon a culture of this organism, two or three died, while others that had fallen sick recovered and the same remained well. This small mortality offered some hope that it would be possible to increase the virulence of the bacillus by ordinary methods; that is, passing it from rat to rat. It was found, however, that the opposite was true; the virulence was always weakened by this process regardless of the method of administration. Thus in every series the first culture killed the animals in seven to twelve days; occasionally after one or two passages five to seven days; but subsequent passages decreased the virulence so that none died.

Footnote BS:

Danysz, J.: Un microbe pathogène pour les rats (Mus decumanus et Mus rattus) et son application à la destruction de ces animaux. Ann. Inst. Pasteur, 1900, vol. 14, p. 193.

The general result is that it is difficult to maintain the virulence of the cocco-bacillus of the rat or to increase it when it is found to be small. It can only be effected by constantly making a large number of experiments and frequently testing the virulence of the culture. Danysz succeeded in keeping up a supply of cultures of sufficient strength for eight years. In 60 per cent of the operations where this culture has been used it has been successful in causing the absolute disappearance of the rats. In 15 per cent the result was entirely negative, and in the remaining 25 per cent there was a large diminution.

Oettinger, in 1903, increased the virulence of the Danysz bacillus by growth in an egg rendered alkaline after the method previously introduced by Wiener.

Footnote BT:

Oettinger, M.: Ueber die Wienersche Methode zur Virulenzsteigerung der Danysz Bazillen. Munch. med. Woch., vol. 1, 1903, p. 324.

Pfreimbtner, 1904, sees the reason for a partial failure in the application of Loeffler’s bacillus to the destruction of field mice. In the use of a solid medium (agar-agar), upon which the bacterial cultures only grow upon the surface, too few bacteria are transferred to the pieces of bread, and consequently too few virulent bacteria are consumed by the mice. An active infection depends not upon the existence of virulent bacteria, but rather upon the entrance of a definite number of virulent bacilli.

Footnote BU:

Pfreimbtner, J.: Erfahrung über des Loeffler’schen Infektionsverfahren zur Bekämpfung der Mäuseplage in einer neuen Art der Anwendung. Fühlung’s landw. Zeit., 1904, p. 619. Rev. by Schander in Centblt. f. Bakt., 2. Abt., vol. 15, 1905, p. 502.

The author used skimmed milk as a nutrient medium and describes a series of 9 experiments and gives an estimate of the cost of the process with the use of milk instead of agar. The advantage of the use of milk is in the greater certainty of the results and cheapness as compared with other methods. The bread cubes impregnated with skimmed milk were well taken by the mice and desiccation of the cultures, which not infrequently occurs in the use of more solid media, is excluded. Notwithstanding the excessive thinning, the liquid still contains many virulent bacilli. The washing out of bacilli after rain is slightly less possible as in the use of the more solid media. The action of light, where the bread cubes contain many bacilli, is insignificant, and hence the carrying out of the process in the daytime is made possible. Milk is easily obtained and the thinning and application less bothersome. Finally the author expresses himself against the view that the B. typhi murium causes serious diseases in man.

Teichert, 1905, speaks of Loeffler’s mice typhus bacillus and Pfreimbtner’s method of growing it upon sterilized skimmed milk. A number of experiments carried out at the bacteriological laboratory of the Vreschen experiment station shows the utility of Loeffler’s bacillus for the destruction of house and field mice. The long-tailed field mouse was, on the other hand, not harmed by it.

Footnote BV:

Teichert: Die mechanischen, chemischen und bacteriellen Kampfmittel gegen Ratten und Mäuse. 2. Teil: Die Bekämpfung der Mäuse. Fühlung’s landw. Zeit., 1905, No. 16. Rev. by Ehrenberg in Centblt. f. Bakt., 2. Abt., vol. 15, 1905, p. 503.

Bahr, 1905, gives a complete and satisfactory summary of the literature upon the subject of the destruction of rats and mice with bacteria, including original work of his own.

Footnote BW:

Bahr, L.: Ueber die zur Vertilgung von Ratten und Mäusen benutzten Bakterien. Centblt. f. Bakt., Orig., vol. 39, 1905, p. 263.

Zielander, 1908, obtained fairly good results with Danysz virus in the laboratory, also with ratin. No fixed tests were recorded.

Footnote BX:

Zielander: Der Rattenbacillus als Rattenvertilgungsmittel. Arb. a. d. k. Gesndhtsmte., Berl., vol. 28, 1908, p. 145.

RÉSUMÉ.

Rats are notoriously resistant to bacterial infection. Even plague usually fails markedly to diminish their prevalence. An epizootic of bacterial nature, therefore, can not be classed with the natural enemies of the rat. We are not surprised, then, to learn that the bacterial viruses have signally failed to accomplish their mission.

These bacterial viruses belong to the colon-typhoid group of organisms. They are either identical with or closely related to the original bacillus of mouse typhoid discovered by Loeffler, or the para-typhoid bacillus type B, which is frequently the cause of meat poisoning, or the Bacillus enteritidis of Gærtner, which has been associated with gastro-intestinal disorders.

The claim that these rat viruses are harmless to man needs revision, in view of the instances of sickness and death reported by various observers. The pathogenicity for man depends upon the virulence of the culture, the amount ingested, the nature of the medium in which it grows, and many other factors.

Danysz virus is pathogenic for rats under laboratory conditions, but has feeble powers of propagating itself from rat to rat. It rapidly loses its virulence, especially when exposed to light and air. The result depends largely upon the amount ingested. The other viruses have proven even less satisfactory.

Under natural conditions these rat viruses may be likened to a chemical poison, with the great disadvantage that they rapidly lose their virulence and are comparatively expensive. They also have the further disadvantage that chemical poisons do not possess of rendering animals immune by the ingestion of amounts that are insufficient to kill or by the ingestion of cultures that have lost their virulence.

PLAGUE ERADICATION IN CITIES BY SECTIONAL EXTERMINATION OF RATS AND GENERAL RAT PROOFING.

By VICTOR G. HEISER,

Passed assistant surgeon, U. S. Public Health and Marine-Hospital Service, chief quarantine officer and director of health for the Philippine Islands.

The health officials of the city of Manila, P. I., for the five-year period from 1900 to 1905 made most valiant efforts to destroy the rats of the city; approximately $15,000 were paid in rat bounties and $325,000 in salaries and wages and other expenses for rat catching, but at the end of that time the rats were apparently as plentiful as before and the plague was still present. The experience in Tokio and Osaka had been practically the same. Professor Kitasato expressed the opinion that a given city could only have up to a certain number anyhow, because further increase was limited by the amount of available food, and when the limit had been reached the rats commenced to eat one another, which prevented more than a certain number ever being present, and that the increase by breeding was about as rapid as any method of destruction which had yet been tried.

The following plan was then tried, and the plague among human beings soon disappeared, there being no cases since April, 1906; and it has been eradicated among rats each time that it has made its appearance.

A list of the places at which plague-infected rats were found was made. Each was regarded as a center of infection. Radiating lines, usually five in number, were prolonged from this center, evenly spaced like the spokes of a wheel. Rats were caught along these lines and examined. Plague rats were seldom found more than a few blocks away. The furthermost points at which infected rats were found were then connected with a line, as is roughly shown in the diagram on page 206 (Fig. 59.)

The space inclosed by the dotted line was regarded as the section of infection. The entire rat-catching force, which had heretofore been employed throughout the city, was then concentrated along the border of the infected section; that is, along the dotted line. They then commenced to move toward the center, catching the rats as they closed in. Behind them thorough rat proofing was carried out. One section after another was treated in this way until they had all been wiped out. Once weekly thereafter rats were caught in the previously infected sections and at other places which were insanitary and which had been infected in years gone by. This was continued for one year.

The city was then divided as is shown in the diagram facing this page, and rats are caught once weekly at each point at which the lines intersect and sent to the laboratory for examination.

FIG. 59.—Isolated plague-infested center, Manila, P. I. ]

In addition, sanitary inspectors are instructed to bring in dead rats which have evidently died of disease, and more detailed rat catchings are made along the water front.

It is understood of course that rat proofing of the entire city should be thoroughly carried out and constantly maintained.

CONCLUSIONS.

1. Since the above system was adopted plague has disappeared in the city of Manila; among human beings in 1906; among rats in 1907, and it has not reappeared since.

2. That the cost is only a small fraction of that of general rat extermination.

3. That the plan is thoroughly practical for any kind of a city.

FIG. 60.—General Scheme for testing plague rat infection, City of Manila. Sanitary Map Bureau of Health. Escala 1:38,500 ]

THE RAT IN RELATION TO SHIPPING.

By WILLIAM C. HOBDY,

Passed Assistant Surgeon, Public Health and Marine-Hospital Service.

Since men first went down to the sea in ships the rat’s voyage-making tendencies have been known, and their fecundity is as well established as their fondness for travel. The record does not state that there were more than a pair on the ark at the beginning of her voyage, but the chances are better than even that her skipper began that voyage with more rats than his manifest showed; but whether he did or not, we can be sure he had more at the end of the voyage than at the beginning. Whether or not succeeding generations inherited from their forbears on the ark this well-known wanderlust is undetermined, but it is a fact that the intimacy and companionship established and begun then have been persistently maintained by the rat ever since. His travels have been coextensive with man’s, until to-day there is not a port on earth where the rat is not present. Any exception to this statement simply proves the rule. The rat is cute; he knows when he is well off and his absence from a port does not prove that he has not been there, but that he has been too intelligent to follow man ashore. In establishing this shipboard intimacy there has been no “by your leave” courtesy on his part either; he goes without consent—against orders, even—and man’s ingenuity has as yet discovered no effective means of keeping him off. This is not surprising when the rat’s ability as a rope walker is considered. I have seen a rat gallop with all appearance of enjoyment along an inclined electric cable from a church steeple on one side of a street into the second story of a hotel on the other. Others have been seen traveling along the telephone wires from house to house, and on shipboard they frequently have runways on small pipes along which they scurry in perfect security. When a ship is fended off 6 feet from the dock and her gang plank is lifted or guarded she is still freely accessible, because all her mooring lines are only so many highways along which rats can and do pass with ease and in perfect safety.

This fondness for ships and sea travel is shared by the various species of the rat family, but the Mus norvegicus has earned the reputation of being the greatest traveler of them all. He almost invariably predominated among those killed by fumigation on shipboard. That he finds life on shipboard easy and the conditions satisfactory is proved by the numbers that are destroyed from time to time by fumigation. While in charge of the outgoing quarantine work in San Francisco the chief engineer of a small lumber carrier called to book his vessel for fumigation. The vessel was small, only 260 tons, and carried nothing but lumber and her own ship’s stores, but the chief declared she was overrun with rats, and to prove it showed where they had eaten the patches from his shoes. He declared they robbed him of his sandwich when he came off watch, and requested me to give her a thorough fumigation. This was done. The next morning the agent of the vessel phoned to ask how I measured rats, stating that on this vessel they had collected “a barrelful and seven.” Three hundred and ten on a little vessel of only 260 tons burthen.

On another vessel after one fumigation 100 were collected immediately after fumigation, but a few days later, when the vessel was undergoing extensive repairs, 425 others were found—a total of 525 on one small vessel. These numbers are small, however, when compared with the results obtained on others, i. e., on grain-carrying vessels. For instance, a vessel was fumigated some years since in Bombay where 1,300 were destroyed at one time, and the Minnehaha, a new vessel only nine months in commission, on fumigation in London, England, in May, 1901, yielded a bag of 1,700 rats.

ADAPTABILITY OF THE RAT TO HIS SURROUNDINGS.

In addition to his qualities as a sailor and tight-rope walker, the rat has the power of adapting himself to most unusual conditions and surroundings. At the beginning of the outgoing work in San Francisco it was urged that rats either could not or would not live on any part of tank ships engaged exclusively in carrying oil, owing to the fumes and vapors that permeated the entire vessel. This statement was unquestionably correct for those compartments in which the oil itself was stored or carried. It was not true, however, for the superstructure of these vessels, for on one of the oil carriers 60 rats were found after one fumigation, and of the thirty or more vessels of this class that were regularly fumigated in San Francisco, although the odors of oil or gasoline were quite strong in the living compartments, not one was found that did not harbor rats. Still more remarkable, as illustrating the rat’s adaptability, was the fact that from the large refrigerating plants which some vessels carried and in which fumigation had not been practiced for a long time rats were obtained that had grown a fur an inch and a half long to protect themselves from the cold.

DAMAGE TO CARGO.

That rats on shipboard in any such numbers as mentioned above must do much damage to cargo can not be doubted.

Inquiry as to the extent of this damage showed that there were no data on the subject. That such damage was common and considerable, however, was revealed by the fact, elicited by these inquiries, that nearly every steamship company on both the Atlantic and Pacific took precautions both to keep rats from getting on board and to destroy them after they did. One example will show what damage may occur. The British steamer Gadsby, on a voyage from India to Antwerp, covering a period of twenty-nine days, had 44,000 out of 46,000 bags of wheat cut by rats, with an estimated damage of $2,200.

The constant and almost universal presence, then, of rats on shipboard can not be doubted, and if it could the results of fumigation, wherever practiced with SO_{2}, would serve to settle the question, for they are found under all conditions, even on the most unlikely vessels.

How do these rodents gain access to a vessel? It has been the custom to assume that they came on board from the docks over the side when this was possible, and when it was not, as when the vessel was fended off or stood too high out of the water, that they made use of the gangways, mooring lines, hawsers, etc., as avenues of communication. It is still the practice, therefore, in enforcing antirat precautions, to compel the ship to fend off 6 feet from the dock, to wear fat funnels on all lines, and to raise the gangway from the dock at night. Just a word as to these precautions. The most practical fender is a floating one made of heavy timbers either bolted together into a solid frame, with the necessary cross braces bolted in, or made up of logs or spars chained together. They should be long enough to distribute the pressure of the vessel as the tide moves over a number of piers or piles so that the weight does not bear, through the medium of these fenders, on just one or two of the wharf foundations. Such a fender will stay in position, will do no damage to the vessel, and no matter how great the amplitude of the tide may be, will always remain below the ship’s gunwale and can not therefore be utilized by rats as a means to get on board. Large vessels require at least two. Small ones need but one, and it was found in San Francisco, in the case of those vessels changing their mooring several times daily, that this one could be carried from wharf to wharf by the vessel without trouble or delay simply by lashing it edgewise outside on top of the guard.

Funnels should be of heavy galvanized iron, circular in shape, and not less than 36 inches in diameter. The spout of the funnel should be 3 inches in diameter and should be at least 18 inches long. The flange of the funnel should be soldered to this 18-inch pipe at its middle so that the spout projects 9 inches out of the funnel and 9 inches into it. When the two halves of the funnel are brought together this spout or tube is occupied by the line or hawser to be protected, and by lashing this tube to the hawser the funnel is held in position and prevented from lying down. Such a funnel should be put on every line from the vessel to the dock, and when the tube does not fit the line the latter should be parceled before the tube is lashed to it.

These, together with raising the gang plank from the dock at night, make up the precautions ordinarily taken to prevent the rats from getting on ships. As stated above, they are based on the assumption that these are the common avenues of entrance. That these precautions do much good can not be doubted, but in the writer’s opinion they do not entirely cover the case, for there remains one other road of ingress, one of the important, if not the most important, which these precautions do not and can not block and through which rats constantly get on board, and that is through the medium of the cargo itself. There is at present nothing to prevent access in this manner to a vessel and the route is so easy that there can be no doubt that whole families of rats are carried on board in this way. In fact some articles of cargo offer inviting harbors and homes to rats, particularly when these articles have been stored for a time in rat-infested warehouses. Among such articles of cargo may be mentioned crockery or china packed in hay or straw or excelsior and loosely crated; various articles of furniture packed in excelsior, wrapped in gunny, and loosely crated; wheat, corn, oats, peanuts, or barley when shipped in bags; and matting in hollow rolls when sewed up in gunny. Any of these articles could easily become the home of even an entire rat family after having been stored for a time prior to shipment in a rat-infested warehouse. As a matter of fact, the last plague rat discovered in San Francisco was found in a bag of peanuts on the third floor of a warehouse.

That rats are thus carried on board is absolutely certain in my opinion. In the recent antiplague campaign at San Francisco there were ample opportunities for observations along this line, and in no other way can the presence of rats in troublesome numbers on board certain vessels be explained. These vessels were new, were freed from rats by careful and repeated fumigation, and between these acts touched at no wharves save in Honolulu and San Francisco, where constant antirat precautions were observed. And yet on their second trip (about five months after the fumigation had been discontinued) they were badly rat-infested. Of course, by no means had all these rats been carried on board in cargo, but the original patriarchs of the colony had, after which, as is probably the case in all rat-infested ships, their natural prolific characteristics did the rest.

In the same way, too, rats are carried from ship to shore and the truth of Kitasatso’s aphorism that “wherever ships go, plague will go,” at once becomes apparent, and any regulations to prevent the introduction of such vermin and the plague which they may carry to be effective must include the inspection of cargo to insure its freedom from rats, this inspection to be made just before it goes on board.

The relation these rodents bear to plague and the part they play in its transmission have been thoroughly discussed and set forth in another article in this work. The work of Ashburton Thompson in Australia and of the British Medical Commission in India was a scientific demonstration that plague was primarily a rat disease transmitted by fleas, while McCoy in the United States has gone further probably than anyone else in demonstrating the manner in which the flea does this work. The importance of this relation is emphasized and the difficulty of ridding a port of pest infection is explained by a fact, first observed so far as I know by Klein, of London, that rats suffer from a chronic form of pest, not fatal, at least for a long time, and during the course of which the rat may exhibit practically his normal activity. This fact then, that plague is primarily a rat disease and that it may occur in the rat in a chronic form, shows how great the danger may be from their presence on shipboard, explains why it is that where ships go plague will go, and emphasizes the importance of destroying them on shipboard apart from the damage and loss which their presence entails.

So important is this and so preeminent is the rôle played by the rat in plague transmission and propagation that I believe regulations should demand that all ships be disinfected at least three times, and better still, four times, a year, for the destruction of rats. If this precaution were taken, and if to it were added an inspection of cargo at the port of embarkation to insure its freedom from rats, I believe the disinfection of cargo could be entirely dispensed with. It is infectious only in so far as it harbors rats, and if these are not present disinfection, in my opinion, does as little good in preventing plague as dipping ballast did in preventing yellow fever.

FUMIGATION.

Once the rat has gained access to a vessel, what is the best method of getting rid of him?

There are several methods, all of which are effective if properly used, and all of which depend on sulphur dioxide as the destructive agent. The following are mentioned: Pot and pan, sulphur furnace, Clayton system, and Marot system. A choice of one of these methods will be determined by the cost, the rapidity of fumigation desired, and the condition of the vessel, whether empty or loaded. No matter which method is selected, to be effective the sulphur dioxide must be simultaneously delivered to or generated in every compartment on the vessel.

For an empty vessel nothing is so satisfactory as the pot and pan method of generating the gas. It has the following advantages; is more rapid than any other, is cheaper, is more effective, and is equally applicable to the largest and the smallest vessel afloat. With a sufficient number of pots and pans 3,500 pounds of sulphur can be burned just as quickly as 100. Ten pounds of sulphur in each of 350 pots will be consumed just as quickly as will 10 pounds in any one of that number, namely, in less than five hours, a fact which was demonstrated over and over in the outgoing work in San Francisco.

At the beginning of this work it was thought a 2½ per cent gas with three hours’ exposure would be sufficient. Practice proved, however, that this was not effective and the strength of gas was increased to 3 per cent and the exposure to five hours which a test, extending over twelve months and embracing over 3,000 vessels, proved to be ample.

The best pot in which to burn sulphur is 6 inches deep, has a flare of 6 inches—that is, the diameter at the top exceeds the diameter at the bottom by that much, is from 16 inches to 24 inches in diameter at the top and has four hemispherical legs about the size of half a billiard ball. These pots when in use are set in a galvanized iron tub. These tubs contain a little water, and are of a diameter 6 inches greater than the top of the pot. The hemispherical legs of these pots will not punch holes into the tub. The pots are filled with sulphur, which is hollowed out into a little crater at the top, into which crater from 4 to 6 ounces of alcohol are poured and when all are ready a lighted match is dropped into each little crater and the compartment is closed.

In actual practice it was found that an exposure of five hours to a 3 per cent gas would not destroy all the rats in absolutely every case. Some ships afford better hiding places than others, and on these an occasional rat would escape. It was the custom, however, to fumigate all vessels every thirty days and after the third fumigation, on vessels that did not carry general cargo, no more rats were obtained, though the fumigations were continued for a number of months.

On those vessels that carried miscellaneous general cargoes a few rats were found after almost every fumigation. These vessels touched no wharf from the time they left San Francisco until their return, except for a short time in Honolulu, where adequate precautions were observed, and it is difficult to understand how these rats got on board if they were not carried on in cargo.

For vessels with cargo in their holds the pot and pan method is dangerous owing to the possibility of fire. For these vessels one of the other methods of generating the sulphur gas must be used. This involves the use of an expensive plant consisting of a furnace, cooling chamber, blower, or fan, and a system of mains and delivery pipes by means of which the gas is delivered to the various holds and compartments of the vessel. To be at all effective the gas must be 4½ per cent strength, with at least twenty-four hours exposure. The one recommendation of such a system is its freedom from danger by fire. It is too slow; the pipes, even where 6 inches in diameter, are liable to clogging with sublimed sulphur, an inevitable result if the fans are driven too rapidly, and it is not possible to do more than one or at most two ships at a time. The inadequacy of such a method when compared to the work done in San Francisco where we averaged over nine vessels every day for almost fourteen months is at once apparent. Many ships now carry their own disinfecting plants, by means of which not only is sulphur dioxide generated and pumped into a compartment, but at the same time also the air of this space is sucked out. This principle is excellent, but in its application the machines used are wholly inadequate, having a very limited sulphur capacity per hour and equipped with delivery pipes in many instances only 2 or 3 inches in diameter. It would be a matter of days to disinfect some of these ships with the machines they carry. In San Francisco we again and again used pots and pans to fumigate these vessels, including the very compartments in which their own machines sat doing nothing.

The Marot system of generating the gas from compressed liquid sulphur dioxide has in this country been found too expensive to apply to vessels. Probably no system will effectually destroy all the rats on a cargo-laden vessel.

SUMMARY.

To summarize then:

1. The rat is found on all vessels, sometimes in enormous numbers, and is able to adapt himself to all sorts of conditions. He either gets on board himself or is carried on in cargo. Owing to his seagoing tendency, his distribution is world-wide.

2. On shipboard, to live he must do damage to either cargo or stores, or both.

3. Plague is primarily a rat disease; it may exist in the rat in a chronic form. Hence where ships go plague will go sooner or later.

4. To prevent the ingress of rats and the consequent spread of plague, ships should observe antirat precautions, and cargo inspection should be included in these.

5. At stated intervals, three or, better still, four times a year, all vessels should be fumigated for the destruction of rats.

6. On empty vessels this can best be done by generating sulphur by the pot and pan method.

7. On laden vessels some special apparatus must be used to generate the gas. A longer exposure is required, at least twenty-four hours, and the gas should be 4½ per cent strength instead of 3 percent. It is extremely difficult by any method to kill all the rats on a cargo-laden vessel.

THE RAT AS AN ECONOMIC FACTOR.

By DAVID E. LANTZ,

Assistant Biologist, United States Department of Agriculture.

INTRODUCTION.

The world has rightly learned to dread rats as disseminators of disease, and recent efforts to rid cities of the pests have resulted chiefly from sanitary considerations. Yet the material losses due to depredations of rats are now, and always have been, a sufficient argument for their destruction. The requirements of sanitation and public health are slowly bringing to pass what economic interests failed to accomplish, namely, a general recognition of the fact that the rat is a standing menace to prosperity. To point out some of the many ways in which rats inflict injury and the extent to which they drain the resources of the people is the object of the present chapter.

UTILITY OF THE RAT.

Do rats serve any useful purpose? With very slight reservation, the question may be answered in the negative. There have been times and places in which the rat’s work as a scavenger accomplished good, but modern methods of garbage disposal are superseding the feeding it to rats.

It was Robert Southey, the poet, who, nearly a century ago, humorously suggested as the first three steps to eradicate rats—first, introducing them as a table delicacy; second, utilizing the skins; and third, inoculating them with a contagious disease. The last of these plans is now receiving considerable attention from bacteriologists, but the others, for obvious reasons, have been neglected.

Footnote BY:

Omniana, vol. 1, p. 25, 1812.

It is true that under exceptional circumstances the rat has been a source of human food. The principal instances on record were during the siege of Paris in 1870, and during the siege of the French garrison at Malta, 1798–1800, when food was so scarce that rat carcasses brought high prices. Another was on board the ship Advance during an arctic winter, when Doctor Kane attributed his entire immunity from scurvy to his diet of fresh rats, of which none of the other members of the party would partake.

Footnote BZ:

Second Grinnell Expedition, vol. 1, p. 393, 1856.

The statement is often made in newspapers, and even in encyclopedias, that in Europe, and especially in France, rat skins are extensively used in the manufacture of gloves. The late Frank T. Buckland, about a half century ago, made diligent inquiry in London, and through friends in Paris and other places on the Continent, but found no confirmation of such statement. He concluded that either rat skins were not used for making gloves or the manufacturers were unwilling to acknowledge such a use. Personally, the writer has been unable to learn of any demand or market for rat skins at the present time. They are not strong, and the fur is of inferior quality. The occasional finding of one or more rat skins in the fur lining of coats is probably to be explained by the fact that they are sometimes included in lots of small muskrat skins (“kitts”) and overlooked by the buyer.

Footnote CA:

Curiosities of Natural History, first series, p. 83, 1857 (Reprint 1900).

DESTRUCTIVENESS OF THE RAT.

Rats inflict injury in a surprising number of ways, and before an attempt is made to consider the magnitude of the losses due to these animals a statement of the nature of their depredations should be made.

DAMAGE TO GRAINS.

Cultivated grains are the favorite food of rats. The animals begin their depredations by digging up the newly-sown seed. They eat the tender sprouts when they first appear, and continue destroying the plants until the crop matures. They then attack the grain itself, and after harvest take toll from shock, stack, mow, crib, granary, elevator, mill, and warehouse. When rats are abundant their depredations amount to an appreciable percentage of the entire yield of grain, and in exceptional cases whole crops have been ruined.

INDIAN CORN.

Probably this crop suffers greater injury from rats than any other in the United States. To some extent the animals dig up newly planted corn, but their injury to the maturing grain is far greater. They are especially fond of corn in the milk stage, and often climb the upright stalks and strip the cobs bare. In this way sometimes whole fields are destroyed.

Corn in the shock is often attacked by rats, especially in parts of fields adjacent to hedges, drains, or embankments that afford shelter for the animals. A pair of rats often make a corn shock their home, and soon destroy both grain and fodder.

Corn in cribs is often damaged by rats. Many cribs are built close to the ground, and rats take up their abode under the floor. They soon gnaw through the wooden barrier and have free access to the grain. They shell the corn and eat the soft part of the kernels, wasting much more than they eat. They carry the grain into underground burrows and bring up moist soil from below, which in contact with the grain makes it moldy and unfit for market or for feeding to stock. A number of farmers have reported the loss by rat depredations of from a fifth to a half of the contents of a large corn crib during a single winter.

An Iowa farmer, writing to an agricultural journal, relates the following experience:

We had about 2,000 bushels of corn in three cribs to which rats ran, and they ate and destroyed about one-fourth of the corn. Much of it was too dirty to put through the grinder until it had been cleaned an ear at a time. All the time we were poisoning and trapping the rats. We killed as high as 300 rats in two days and could hardly miss them. They destroyed more than enough corn to pay taxes on 400 acres of land.

Footnote CB:

Missouri Valley Farmer, April, 1907.

Throughout the United States, but especially in the West and South, corn is often stored for months in rail or other open pens, to which rats have free access. Often the loss in a single season would pay for the construction of rat-proof cribs, or at least for wire netting, that would fully protect the crop.

SMALL GRAINS.

Much has been written about the rat as a house and barn pest, but its depredations in the fields have usually been overlooked. In some localities the common rat, as well as the house mouse, swarms in the fields, especially in summer, and subsists entirely upon the farmers’ crops.

Stacked grain is peculiarly exposed to rat depredations. In the United States, although the cost of protection is small, rats are seldom fenced away from stacks, and, if threshing is delayed, serious loss results. Often, at the removal of a stack, large numbers of rats are discovered, which have been living at the expense of the farmer. As early as 1832 a farmer in Frederick County, Md., with the help of men and dogs, killed 217 large brown rats from one stack of rye. In England instances are on record of the killing of over a thousand rats from one stack of wheat.

Footnote CC:

Am. Turf. Register, vol. 3, p. 632, August, 1832.

The destruction of feed by rats is a serious loss not only on the farm but also in city and village. The feed bin or barrel is often left uncovered and rats swarm to the banquet thus exposed. Small feeders suffer greater proportional losses, for managers of larger barns recognize the enormous drain and usually provide rat-proof bins, if not rat-proof stables. When rats have access to a stable they take a good share of the feed directly from the mangers, but the loss is seldom noticed.

Rats are exceedingly fond of malt, and in malt houses and breweries constant watchfulness is needed to prevent losses. Mills, elevators, and warehouses in which grain and feed stuffs are stored are subject to constant invasion by rats and mice.

A full-grown rat consumes about 2 ounces of grain daily. A half-grown rat eats nearly as much as an adult. Fed on grain, therefore, a rat eats from 45 to 50 pounds a year. The cost depends somewhat on the kind of grain. If wheat, the value is 60 to 75 cents; if oatmeal, about $1.80 to $2. Several feeders of horses in Washington, D. C., estimated the cost of keeping each rat on their premises at $1 a year. Even though half the grain eaten is waste, the direct loss from this source to feeders is enormous.

MERCHANDISE IN STORES AND WAREHOUSES.

The loss from depredations of rats on miscellaneous merchandise in stores, markets, and warehouses, is second only to the losses on grains. Not only are food materials of every kind subject to attack, but the destruction of dry goods, clothing, books, leather goods, and so on is equally serious. Merchandise other than foodstuffs is usually destroyed for making nests, but books and pamphlets, especially the newly bound, and some other articles, furnish food in the glue, paste, oils, or paraffin used in their manufacture. Some kinds of leather have a peculiar attraction for rats, while others are never touched. Shoes are seldom gnawed unless they have cloth uppers or are made of kid. New harnesses are not often attacked, except collars, which contain straw, and cruppers, which are stuffed with flaxseed. Old harness leather is salty from the perspiration of horses, and rats and mice gnaw it for this reason. Kid gloves and other articles made of similar leather are often destroyed by rats.

Lace curtains, silk handkerchiefs, linens, carpets, mattings, and other dry goods in stores are often attacked by rats. Some of the stuffs contain starch, which serves as food, but most of them furnish nesting materials only. A slight injury makes these articles unsalable; this is especially true of white goods, which are easily ruined by soiling. Nearly all large dry goods and department stores suffer heavy losses from rats. Grocers, druggists, confectioners, and other merchants also have similar experiences, and to the direct losses must be added the sums expended in fighting the pests.

MERCHANDISE IN TRANSIT.

Merchandise billed for shipment often lies for days in stations and warehouses or on wharves, where depredations of rats and mice cause heavy losses to shippers and consignees. Similar losses occur on boats carrying merchandise from port to port.

Fruits and vegetables in transit on steamboats are often destroyed or damaged by rats. Tomatoes, cucumbers, sweet potatoes, bananas, oranges, grape fruit, peanuts, and similar produce shipped by water from the South, especially in winter, reach northern markets with a large percentage of loss.

In view of the practicability of destroying rats on ships by fumigation, and the ease with which rat-proof compartments for stowing produce can be constructed, it would seem that losses of this nature should be entirely prevented.

POULTRY AND EGGS.

Aside from disease, the greatest enemy of poultry is the rat. The loss from rats varies with their abundance and the care taken to exclude them from the poultry yard. The magnitude of the damage is not generally known, because much of it is blamed on other animals, particularly minks, skunks, and weasels. Much of the injury occurs at night, and the actual culprit is seldom detected. Farmers have heard that minks, skunks, and weasels prey upon poultry. What more natural than to conclude that one of these animals is doing the mischief, especially if one has been seen about the premises?

Rats often prey upon small chicks, capturing them in the nests at night or even about the coops in the daytime. The writer has known rats to take nearly all the chicks on a large poultry ranch, and over a large section of country to destroy nearly half of a season’s hatching. Young ducks, turkeys, and pigeons are equally liable to attack, and when rats are numerous, are safe only in rat-proof yards.

A writer in a western agricultural journal states that in 1904 rats robbed him of an entire summer’s hatching of three or four hundred chicks. A correspondent of another newspaper says, “Rats destroyed enough grain and poultry on this place in one season to pay our taxes for three years.” When it is remembered that the poultry and eggs marketed each year in the United States have a farm value of over $600,000,000, it will be seen that a small percentage of loss represents an enormous sum.

Footnote CD:

Homemaker (Des Moines, Iowa), May 27, 1907.

Footnote CE:

Missouri Valley Farmer, April, 1907.

The destruction of eggs by rats is great, not only on the farms where they are produced, but also in the markets. Commission men and grocers complain of depredations upon packed eggs. The animals break and eat a few eggs at the top of a case and the broken yolks run down and soil the eggs below. Then, too, rats carry away unbroken eggs, displaying much ingenuity in getting them over obstacles, as up or down a stairway.

A commission merchant in Washington, D. C., states that he once stored 100 dozen eggs in a wooden tub in his warehouse and left them for nearly two weeks. He then found that rats had gnawed a hole through the tub, just under the cover, and had carried away 71½ dozen, leaving neither pieces of shell nor stains to show that any had been broken.

Besides their destruction of eggs and young fowls, rats eat much of the food put out for poultry. They are destructive also to tame pigeons and their eggs, but particularly to young squabs. They climb the wire netting and gain entrance to the cages through the same openings by which the pigeons come and go. Fanciers are often put to great trouble to protect their pigeons from rats, and because of these pests some of them have abandoned the business.

GAME AND WILD BIRDS.

The rat is the most serious pest in European game preserves. A writer in Chambers’s Journal says:

In a closely preserved country at the end of an average year the game suffers more from the outlying rats of the lordship than from the foxes and mustelines together. The solitary rats, whether males or females, are the curse of a game country. They are most difficult to detect, for in a majority of cases their special work is supposed to be done by hedgehog, weasels, or stoat.

Footnote CF:

Chambers’s Journal, vol. 82, p. 64, January, 1905.

The propagation of game birds is becoming a promising industry in the United States. The difficulties of the business are not yet fully known, but the rat is an enemy with which the raiser of game will have to contend. The animal has already proved itself a foe in American pheasantries.

Our wild native game birds are less subject to rat depredations than birds kept in confinement. The nests of ruffed grouse are in woodlands; those of the prairie hen and related species are on plains remote from the haunts of rats. The quail, however, often makes its nest within the summer range of rats, which destroy many of its eggs.

Rats are said often to destroy the nests of wild ducks, woodcock, and other marsh birds. Terns have been entirely driven from their nesting grounds in this way. In England the common tern was extirpated from the Thames marshes; and on Loggerhead Key, Tortugas Islands, off the Florida coast, rats recently nearly exterminated a colony of least terns by destroying the eggs.

The nests of many ground-nesting and other song birds are robbed by rats. Crows, jays, snakes, and skunks are blamed for most of the destruction and the actual offender seldom suspected. While the other animals named do part of the mischief, the rat is a more serious foe of song and game birds than any of these.

FRUITS AND VEGETABLES.

A well-known form of damage by rats is the destruction of fruits and vegetables in cellars and pits. Apparently no garden vegetable or common fruit is exempt from attack. But the rat does not confine its depredations to stored fruits and vegetables. It attacks ripe tomatoes, melons, cantaloupes, squashes, pumpkins, sweet corn, and many other vegetables in the field; and often the depredations are attributed to rabbits or other animals, which may or may not be concerned in the mischief.

Rats are fond of the small fruits, eating not only the fallen but climbing vines and canes to obtain the ripe grapes or berries. They eat also apples, pears, cherries, and other fruits. The brown rat, while not so expert as the black or the roof rat, readily climbs trees and obtains fruit even at the extremities of the branches.

Among tropical fruits injured by rats are oranges, bananas, figs, dates, cocoanuts, and especially the pods of cacao (Theobroma cacao), from which chocolate is manufactured. H. N. Riddey, writing of his experiences on the island of Fernando do Noronha, South America, mentions the destructiveness of rats in this penal colony. They climb the cocoanut palms and papaw trees to devour the fruit, and do mischief in melon patches. To lessen the evil, each convict was required to bring in a certain number of dead rats, and battues were held monthly to satisfy the requirement. Sometimes the number killed in a single hunt reached 20,000.

Footnote CG:

Zoologist, vol. 46, p. 46, 1888.

Fruits and vegetables grown under glass are subject to injury by rats. The animals usually find entrance to greenhouses by way of openings for pipes or drains.

FLOWERS AND BULBS.

Rats attack seeds, bulbs, and the leaves, stems, and flowers of growing plants, whether in the greenhouse, propagating pits, or elsewhere. Of flowering bulbs, the tulip suffers most from rats. Hyacinths also are eaten; but, probably because they are slightly poisonous, narcissus and daffodil bulbs escape injury. Rats eat pinks, carnations, and roses, cutting the stems off clean. They denude geraniums of both flowers and leaves. They attack the choicest blooms of chrysanthemums and carnations in markets, stores, and exhibition rooms, causing heavy losses.

FIRES.

Rats and mice cause many fires. Several specific instances have been reported by the fire department of the city of Washington within the past two or three years. It is likely that some of these fires are caused by rats gnawing matches. The animals are fond of paraffin, which is often used to protect match heads. They carry the matches to their nests, which are composed of paper and other combustible materials, and the conditions for a conflagration are ready. Since the heads of matches contain from 14 to 17 per cent of phosphorus, actual gnawing is not required to ignite them, but heat or friction from any cause may suffice.

Fires in mills or warehouses have sometimes been traced to the spontaneous ignition of oily or fatty rags and waste carried under floors by rats. Cotton and woolen mills are said to be peculiarly subject to fires of this kind.

Sometimes rats cause fires by gnawing through the lead pipes leading to the gas meter. Workmen or others, searching for the leak, accidentally ignite the gas. Phillips’s warehouse, London, was twice badly damaged by fires originating in this way, and in several instances the sleeping inmates of houses have been in danger of asphyxiation by gas freed in this manner.

The most common way in which rats and mice cause fires is by the destruction of the covering of electric light wires under floors or in partition walls. A considerable percentage of the enormous fire losses in the United States is caused by defective insulation of wires. After wires are once in position rats are the chief agents in impairing the insulation. These animals do much mischief also by gnawing off the coverings of telephone wires. In the case of electric light wires the covering is probably used by the rats for nesting material, but frequently the paraffin in the insulation is the object of attack.

BUILDINGS AND FURNITURE.

Rats seem to be able to gnaw through almost any common material except stone, hard brick, cement, glass, and iron; neither wood nor mortar suffice to keep them out of bins or rooms. They sometimes gnaw through walls or doors in a single night. In the same way they enter chests, wardrobes, bookcases, closets, barrels, and boxes. Almost every old dwelling bears evidence of its present or former occupancy by rats. Often the depreciation of houses and furniture is largely due to marks left upon them by rats—marks that paint and varnish can not hide.

Damage to dwellings by rats is a large item. The decay of sills and floors is hastened by contact with moist soil brought up from rat burrows. Ceilings, wall decorations, and floor coverings are flooded by leaks in lead pipes or wooden tanks gnawed by rats. Bricked areas and even foundations are undermined and ruined by rats. All this is real waste and a constant drain on the resources of the country.

MISCELLANEOUS.

A few instances of miscellaneous damage by rats may be mentioned to show the great variety of mischief chargeable to the animals.

A Washington, D. C., merchant reported that at one time rats in his store destroyed 50 dozen brooms worth $2.50 a dozen. In another store, in a single night, they broke $500 worth of fine chinaware on shelves and tables. A dealer in harness reported the loss of $400 worth of collars in one season. The manager of a restaurant complained of an average loss of $30 a month in table linen ruined by rats and mice. A hotel reported the destruction of $75 worth of linen in a month.

At Mobile, Ala., in March, 1908, lost jewelry worth $400 was recovered from a rat’s nest in the home of Señor Viada.

In London rats at one time killed all but 11 out of an aviary of 366 birds.

At Hamburg, Germany, Carl Hagenbeck once had to kill three young African elephants because rats had gnawed their feet, inflicting incurable wounds.

Rats often gnaw the hoofs of horses until they bleed. They kill young lambs and pigs, and have been known to gnaw holes in the bodies of very fat swine, causing death.

Like the muskrat, the brown rat often burrows into embankments and dams, causing serious breaks.

The rat is one of the greatest enemies with which the sugar planter has to contend, destroying acres of growing cane.

In rice plantations rats not only break down and destroy the growing crops, but burrow into the dikes and flood the fields at the wrong season.

On the London docks and on shipboard ivory is often badly damaged by rats. They select for attack the greenest tusks, which are the more valuable.

Mail sacks and other kinds of bagging are greatly injured by rats. The consequent loss and necessary outlay for repairs are a large item in post-office expenditures and in mills and other places where bagging is used.

About the year 1616 rats caused a two years’ famine in the Bermudas. In the southern Deccan and Mahratta districts of India rats ate a large part of the scant crops of 1878 and 1879, and were regarded as in a great measure responsible for the severe famine which followed. A writer in Chambers’s Journal stated that the Dutch abandoned the Isle of France (Mauritius) in 1610 because of the great abundance of rats.

Footnote CH:

Brit. Med. Journ., p. 623, September 15, 1905.

Footnote CI:

Chambers’s Journal, vol. 21, p. 244, 1854.

AMOUNT OF LOSSES CAUSED BY RATS.

The damage done by a single rat varies greatly with the circumstances. We have already stated that the cost of feeding a rat on grain varies from 60 cents to $2 a year. Assuming that much of the rat’s food is waste, each rat on a farm will cause a loss of over 50 cents a year. In cities the damage by a single rat probably averages more than in the country. Hotel managers and restaurant keepers state that $5 a year is a low estimate of the loss inflicted by a rat. In making an estimate it should be remembered that the rat is to be charged not only with the food it actually consumes but also with what it destroys or pollutes and renders unfit for use.

If an accurate census of the rats in the United States were possible, and if the minimum average loss caused by a rat were known, an estimate of the total annual losses from their depredations could be made. It was on such a minimum basis that the Incorporated Society for the Destruction of Vermin arrived at their total estimate of £15,000,000 ($73,000,000) as the yearly losses from rats in Great Britain and Ireland. Three propositions were assumed: first, that in cities and villages the number of rats equals the population; second, that in the country there is at least one rat for every acre of cultivated land; third, that each rat in the kingdom inflicts a damage of at least a farthing per day. Circulars asking whether these assumptions are excessive were distributed throughout the country. From 90 to 99 per cent of the replies fully indorsed each of the assumptions.

It can readily be seen that the English basis of estimate would not apply to farm conditions in the United States, where the area in the twelve leading crops alone is over 250,000,000 acres. On a basis of a rat per acre and damage of a farthing per day the annual loss on this area would be $450,000,000, a sum much too great for serious consideration. However, in the more thickly populated parts of the country an estimate of one rat per acre would not be excessive; and it is probable that in most of our cities there are quite as many rats as people. Yet it would be unsafe, owing to our vast territory and varying conditions, to make these assumptions the basis for conclusions.

Over a year ago the writer made an attempt to investigate actual conditions, and thus arrive at an estimate of the total damage by rats in the cities of Washington and Baltimore. From the data obtained the direct annual damage in the two cities was calculated at $400,000 and $700,000, respectively. The Census Bureau in 1906 estimated the population of these cities at 308,000 and 554,000, respectively. If the estimates of damage were correct, the average loss for each person is $1.27 a year; and, on the same basis, the 28,000,000 of urban population in the United States (census of 1900) sustains an annual direct injury of $35,000,000 from rats. This is considerably lower than on the English assumption, which would make the losses in our cities over $50,000,000.

Denmark (population 2,500,000) has an estimated rat bill of about $3,000,000 a year, or $1.20 a person. Germany (population 56,000,000) is said to sustain a loss from rats of 200,000,000 marks ($47,640,000) a year, or about 85 cents for each person. The per capita estimate for the United Kingdom is about double that made for Germany. In France the loss from rats and mice for a single year (1904) was placed at $38,500,000, or a little over a dollar for each of its 38,000,000 inhabitants. These estimates are supposed to include only direct losses, but they vary enough to show that no common basis can be assumed for all countries. With present information, therefore, any attempt to state the amount of loss from rats in the United States would be largely guesswork. Considering the population and wealth of the country, however, and the vast area over which rats are abundant, it is not unreasonable to conclude that in the United States the losses from rats amount to much more than in any of the other countries named.

INDIRECT LOSSES.

To the direct losses caused by rats must be added the cost of fighting the animals and of protecting property from them. In our larger cities a number of so-called expert rat catchers are to be found, who operate with dogs, ferrets, traps, poisons, or other means, and who have an extensive clientage among merchants, hotel managers, and others. These pay the rat catcher a yearly or monthly stipend to keep their premises free of rats and mice. Some of the large establishments pay $200 to $600 yearly for such service. While the agreements are seldom kept in full, the clients are usually satisfied that results warrant the expense. Even when no contractor is employed, merchants are at expense for traps, poisons, the keep of cats or dogs, and other means of fighting rats. The same is true in less degree of nearly every householder.

The cost of protecting property from rats is no small item. It increases the expense of nearly all building, but it greatly reduces direct losses from the animals. The economy of rat-proof construction is everywhere manifest, in city or country, and the necessity for it can not be too strongly emphasized.

Depreciation of property and loss of rents and custom are items not generally thought of in connection with rat damage. A few years ago the writer knew of almost an entire block of city houses that remained untenanted for several months, because infested by rats. As the houses were otherwise desirable, the loss of rent to the owners was probably nearly $2,000. The presence of rats in markets, hotels, and restaurants inevitably results in loss of custom, besides the direct damage by the rodents.

From every point of view the keeping of rats is exceedingly expensive, and the sooner our population can be made to realize the enormous drain upon our resources caused by these rodents the sooner can concerted measures for their destruction be made effective.

THE RAT IN RELATION TO INTERNATIONAL SANITATION.

By Asst. Surg.-Gen., JOHN W. KERR,

Public Health and Marine-Hospital Service.

Rats, like man, had their origin in Asia, from which continent they have finally become disseminated throughout the world. They, too, like man, are great travelers, and therefore prey on the commerce of the ships in which they are carried. For this reason, and on account of the fact that they are subject to plague and may transmit the disease from one country to another, these animals have an influence on international policy, and their control aboard ships is an international problem.

It has been estimated that there are as many rats as there are human beings, and that each rat causes each day a loss by the destruction of material of at least half a cent.

Assuming that the rat population aboard ships is as great as the human population—and my experience gained during the fumigation of ships to kill rats convinces me that on the whole it is greater—some idea may be had of the enormous migrations of rats and the toll they exact for food from international commerce. Some idea can also be had of the danger of rats in transmitting plague when it is remembered that 51 countries have been infected with the disease since the present pandemic began in Canton, China, in 1894, and when it is known that at least 146 ships have had plague infection on board during that time.

During the International Sanitary Conference of Paris in 1903 the influence of the rat in transmitting plague was borne in mind, and the international sanitary agreement, which was signed ad referendum December 3, 1903, requires the destruction of rats aboard plague-infected ships, recommends it on ships suspected of being plague infected, and permits it on ships indemne from plague. The ship is considered indemne from plague which, although coming from an infected port, has had neither death nor case on board either before departure, during the voyage, or at the moment of arrival.

The International Sanitary Convention signed at Washington, October 14, 1905, follows the text of the Paris convention, with respect to plague, consequently embodying similar requirements and recommendations as follows:

ART. XX. Classification of ships.—A ship is considered as infected which has plague, cholera, or yellow fever on board, or which has presented one or more cases of plague or cholera within seven days, or a case of yellow fever at any time during the voyage.

A ship is considered as suspected on board of which there have been a case or cases of plague or cholera at the time of departure or during the voyage, but no new case within seven days; also such ships as have lain in such proximity to the infected shore as to render them liable to the access of mosquitoes.

The ship is considered indemne which, although coming from an infected port, has had neither death nor case of plague, cholera, or yellow fever on board, either before departure, during the voyage, or at the time of arrival, and which in the case of yellow fever has not lain in such proximity to the shore as to render it liable, in the opinion of the sanitary authorities, to the access of mosquitoes.

ART. XXI. Ships infected with plague are to be subjected to the following regulations:

1. Medical visit (inspection).

2. The sick are to be immediately disembarked and isolated.

3. Other persons should also be disembarked, if possible, and subjected to an observation, which should not exceed five days, dating from the day of arrival.

Footnote CJ:

The word “observation” signifies isolation of passengers, either on board ship or at a sanitary station, before being given free pratique.

4. Soiled linen, personal effects in use, the belongings of crew and passengers which, in the opinion of the sanitary authorities are considered as infected, should be disinfected.

Footnote CK:

The term “crew” is applied to persons who may make, or who have made, a part of the personnel of the vessel and of the administration thereof, including stewards, waiters, “cafedji,” etc. The word is to be construed in this sense wherever employed in the present convention.

5. The parts of the ship which have been inhabited by those stricken with plague, and such others as, in the opinion of the sanitary authorities, are considered as infected, should be disinfected.

6. The destruction of rats on shipboard should be effected before or after the discharge of cargo, as rapidly as possible, and in all cases with a maximum delay of forty-eight hours, care being taken to avoid damage of merchandise, the vessel, and its machinery.

For ships in ballast, this operation should be performed immediately before taking on cargo.

ART. XXII. Ships suspected of plague are to be subjected to the measures which are indicated in Nos. 1, 4, and 5 of Article XXI.

Further, the crew and passengers may be subjected to observation, which should not exceed five days, dating from the arrival of the ship. During the same time the disembarkment of the crew may be forbidden, except for reasons of duty.

The destruction of rats on shipboard is recommended. This destruction is to be effected before or after the discharge of cargo, as quickly as possible, and in all cases with a maximum delay of forty-eight hours, taking care to avoid damage to merchandise, ships, and their machinery.

For ships in ballast this operation should be done, if done at all, as early as possible, and in all cases before taking on cargo.

ART. XXIII. Ships indemne from plague are to be admitted to free pratique immediately, whatever may be the nature of their bill of health.

The only regulation which the sanitary authorities at a port of arrival may prescribe for them consists of the following measures:

1. Medical visit (inspection).

2. Disinfection of soiled linen, articles of wearing apparel, and the other personal effects of the crew and passengers, but only in exceptional cases when the sanitary authorities have special reason to believe them infected.

3. Without demanding it as a general rule, the sanitary authorities may subject ships coming from an infected port to a process for the destruction of the rats on board before or after the discharge of cargo. This operation should be done as soon as possible, and in all cases should not last more than twenty-four hours, care being taken to avoid damaging merchandise, ships, and their machinery, and without interfering with the passing of passengers and crew between the ship and the shore. For ships in ballast this procedure, if practiced, should be put in operation as soon as possible, and in all cases before taking on cargo.

When a ship coming from an infected port has been subjected to a process for the destruction of rats, this process should only be repeated if the ship has touched meanwhile at an infected port, and has been alongside a quay in such port, or if the presence of sick or dead rats on board is proven.

The crew and passengers may be subjected to a surveillance, which should not exceed five days, to be computed from the date when the ship sailed from the infected port. The landing of the crew may also, during the same time, be forbidden except for reasons of duty.

Competent authority at the port of arrival may always demand, under oath, a certificate of the ship’s physician, or in default of a physician, of the captain, setting forth that there has not been a case of plague on board since departure, and that no marked mortality among the rats has been observed.

ART. XXIV. When upon an indemne ship rats have been recognized as pest stricken as a result of bacteriological examination, or when a marked mortality has been established among these rodents, the following measures should be applied:

1. Ships with plague-stricken rats:

(a) Medical visit (inspection).

(b) Rats should be destroyed before or after the discharge of cargo, as rapidly as possible, and in all cases with a delay not to exceed forty-eight hours; the deterioration of merchandise, vessels, and machinery to be avoided. Upon ships in ballast, this operation should be performed as soon as possible, and in all cases before taking on cargo.

(c) Such parts of the ship and such articles as the local sanitary authority regards as infected, shall be disinfected.

(d) Passengers and crew may be submitted to observation, the duration of which should not exceed five days, dating from the day of arrival, except in special cases, where the sanitary authority may prolong the observation to a maximum of ten days.

2. Ships where a marked mortality among rats is observed:

(a) Medical visit (inspection).

(b) An examination of rats, with a view to determining the existence of plague, should be made as quickly as possible.

(c) If the destruction of rats is judged necessary, it shall be accomplished under the conditions indicated above in the case of ships with plague-stricken rats.

(d) Until all suspicion may be eliminated, the passengers and crew may be submitted to observation, the duration of which should not exceed five days, counting from the date of arrival, except in special cases, when the sanitary authority may prolong the observation to a maximum of ten days.

ART. XXV. The sanitary authorities of the port must deliver to the captain, the owner, or his agent, whenever a demand for it is made, a certificate setting forth that the measures for the destruction of rats have been efficacious and indicating the reasons why these measures have been applied.

To be in conformity with these agreements regarding the destruction of rats, quarantine authorities may demand the fumigation of infected and suspected ships; suspected ships within the meaning of the treaties being those on board of which there have been a case or cases of plague at the time of departure or during the voyage, but no new case within seven days. In the case of indemne ships, on the other hand, without demanding it as a general rule, the sanitary authorities may subject them to fumigation to kill rats. When upon such ships rats have been recognized as pest stricken, as a result of bacteriological examination, or when a marked mortality has been established among these rodents, fumigation is prescribed.

While the classification of ships and the limitations placed on quarantine procedures in relation thereto, as contained in existing international sanitary agreements, is more apparent than real, there appears to be a lack of exactness with respect to the destruction of rats necessary for the prevention of the importation of plague from one country to another.

Since the adoption of the international sanitary agreement of Paris in 1903, some of the unproven convictions of that time regarding the rôle of rats and fleas in the transmission of plague have been proven to be positive facts. Many epidemiological observations and exact scientific experiments have demonstrated particularly the importance of the rat in the propagation of plague and the rôle of the flea as the carrier of infection from rat to rat and from rats to man.

At the same time there has been a growing conviction that other agencies, such as passengers, baggage, and merchandise play a very minor rôle in the dissemination of plague. It is of interest, therefore, to review the efforts being made at the more important seaports to exterminate rats, as well as the methods being employed to that end.

INQUIRY INTO THE CRUSADE AGAINST RATS THROUGHOUT THE WORLD.

The first law in modern times aiming at the destruction of rats appears to have been enacted in Barbados in 1745. According to Boelter this act was incorporated into a new act which was passed in 1748. The same author states that the next legislative body to enact a law against rats was in Antigua in 1880. In the same article he refers to the rat ordinance of Hongkong, adopted in 1902.

Footnote CL:

W. R. Boelter, “On Rat Laws,” Journal of Incorporated Society for the Destruction of Vermin, October, 1908.

Private measures against rats have undoubtedly been practiced from time immemorial. The action of Denmark, however, in passing a law for the systematic destruction of rats and providing the organization for that purpose is perhaps the most notable advance taken on this subject. A copy of the Danish law appears elsewhere in this publication.

That the citizens of other countries are equally alive to the importance of rat extermination is shown by the fact that in England there exists an incorporated society for the destruction of vermin, which society in October, 1908, began the publication of a journal which would supply trustworthy information upon the subject.

It is recognized that a detailed review of past efforts against rodents would be unprofitable, but on account of the enormous trade relations between important seaports it is thought that a review of the measures taken therein against rodents would be of value.

RAT EXTERMINATION IN UNITED STATES PORTS.

Prior to the adoption of the International Sanitary Conventions of Paris and Washington, the Federal Government had made provision in its quarantine regulations for the prevention of the spread of plague on ships through rodents.

The articles contained in the United States Quarantine Regulations, issued April 1, 1903, and bearing on the subject, are as follows:

14. At ports or places where plague prevails every precaution must be taken to prevent the vessel becoming infected through the agency of rats, ants, flies, fleas, or other animals. At such ports or places the vessel should not lie at a dock, or tie to the shore, or anchor near any place where such animals may gain access to the vessel. In case cables are led to the shore they should be freshly tarred and provided with inverted cones or such other devices as may prevent rats and other animals passing to the ship. The introduction of vermin on board the vessel from lighters and all other sources should be guarded against. In such ports sulphur fumigation should be resorted to in the holds when empty and from time to time during loading in order to destroy vermin.

45 (b) Free ventilation and rigorous cleanliness should be maintained in all portions of the ship during the voyage and measures taken to destroy rats, mice, fleas, flies, roaches, mosquitoes, and other vermin.

45 (h) In the case of plague, special measures must be taken to destroy rats, mice, fleas, flies, ants, and other vermin on board.

128. Vessels infected with plague, or suspected of such infection, should be anchored at a sufficient distance from the shore or other vessels to prevent the escape of rats by swimming.

133. Special precautions must be taken against rats, mice, ants, flies, fleas, and other animals, on account of the danger of the infection of the disease being spread through their agency.

134. As soon as practicable there shall be a preliminary disinfection with sulphur dioxide for the purpose of killing rats and vermin before further disinfecting processes are applied to the vessel and her cargo. The killing of any escaping rats shall be provided for by a water guard in small boats, and no person with abrasions or open sores should be employed in the handling of the vessel or her cargo.

135. The vessel shall be submitted to a simultaneous disinfection in all parts with sulphur dioxide to insure the destruction of rats and vermin. The rats shall be subsequently gathered and burned, due precautions being taken not to touch them with the bare hands, and the places where found disinfected with a germicidal solution; and the quarantine officer shall assure himself that the vessel is free of rats and vermin before granting free pratique.

Additional regulations prescribe the method of disinfection of vessels for plague, and elsewhere in this publication is given a detailed description of the measures taken aboard ships at Angel Island, one of the national quarantine stations.

Elsewhere is also given an account of the measures taken to eradicate plague from certain cities on the Pacific coast, among the measures being the systematic destruction of rodents and practical rat proofing.

In a letter dated November 21, 1908, requests were made to the Department of State for reports from certain of the more important foreign seaports as to systematic measures being practiced for the destruction of rats. As a result much valuable information has been received, and acknowledgments are due and here made to the consular officers furnishing it. The data received was abstracted and classified according to countries as follows:

RAT EXTERMINATION IN CHINESE CITIES.

Although the present pandemic of plague had its origin in Canton, China, in 1894, and the disease has been endemic there practically ever since, Consul-General Bergholz states that the provincial government of Kwangtung has made no efforts to exterminate rats.

In Amoy the local authorities have never taken measures to encourage the extermination of rats, and in the absence of assistance from the local authorities but little can be done toward effective eradication.

An outbreak of plague in Shanghai in December, 1908, was attributed to the introduction of rats by ships from plague-infected ports. A plan of campaign for such an emergency had previously been formulated and was put in operation. It included collection and laboratory examinations of rats and organization of rat parties to destroy rats and render houses rat proof.

Footnote CM:

The Municipal Gazette, Shanghai, January 7, 1909, Health Officer’s report for December, 1908.

In Tientsin official efforts made to exterminate rats are on lines to suit the convenience of the particular health official. The consulate at that port states that generally on the appearance of plague, the officials pay about one-half cent for each rat brought, and as the epidemic becomes severe, as much as 2½ cents gold.

In Hongkong, the question of rats in relation to plague has been of perennial interest. While on duty in the American consulate at that port, my attention was forcibly called to the influence of rodents in the transmission of plague. In 1900 it had been the practice to encourage the destruction of rats in the city, and a reward of 2 cents Mexican money was offered for each rat brought to the health department. A certain number of these rats were examined from day to day from different districts.

In August, 1901, arrangements were made by which the health department collected and examined a specified number of rats each day to try to determine in some degree the relative prevalence of plague among these animals. This practice was continued for several months, with the result that the mortality among rodents from the disease was shown to have rapidly decreased until in November practically no plague-infected rats were found.

In a discussion of the subject, furnished February 2, 1909, by Dr. W. W. Pierce, medical officer of health, through Consul-General A. P. Wilder, it is stated that in 1902 the fee for rats was raised to 5 cents, and a special staff of coolies was engaged to destroy rats. The abuses on account of these bounties were so great, however, that it was found necessary to discontinue it in 1903, but the method of trapping rats was continued.

While the total number of rats taken in 1903 was 101,047, Doctor Pierce stated in effect that on account of the prejudice against disinfection, it was practically impossible to secure the addresses where the infected rats were found. The services of the staff were continued, however, until 1908, when they were abolished because it was thought, as stated by Doctor Pierce, that results were not commensurate with the cost, and many complaints were heard. The plan of furnishing traps to all persons who applied was then introduced, and in addition, structural methods which had gone on for years were continued.

The traps were distributed through district committees consisting of the more educated natives, who were informed that with their assistance it would be possible to avoid abuses which had been practiced by the official rat-catching staff.

Doctor Pierce stated that it had been impossible under other systems to secure the addresses where infected rats were found, and in order to overcome this prejudice, several hundred receptacles were placed in different parts of the city whereby the rats could be collected. These tins were visited from day to day, and by this means it was possible to locate infected districts.

Doctor Pierce stated that the use of ordinary disinfectants in plague-infected houses had been discontinued, and that a 2 per cent mixture in water of a kerosene emulsion made by stirring warm tank oil, 85 parts added gradually to 15 parts of hot, strong solution of “sunlight” soap, was used. This solution was found to instantly kill fleas and bugs, and it has been used systematically.

For ordinary cleansing a 1 per cent solution is used, but Doctor Pierce stated that on the recurrence of plague special gangs would be employed to apply a 2 per cent solution in infected localities.

Beginning with January 1, 1909, Doctor Pierce stated that a rat poison known as “Punjaub rat exterminator” had been laid down, and that the intensive destruction of rats by this means was under consideration.

In summarizing the measures taken against rats, the American consul-general stated that four methods were in use, namely, rat proofing, trapping, poisoning, and use of cats. The use of bacterial viruses as poisons has thus far been unsatisfactory, and the use of chemical poisons, such as phosphorus, prepared, and known as “Punjaub rat exterminator,” has only given moderate results.

The keeping of cats is encouraged, and the consul states that some hundreds of these animals have been imported from Macao and Canton by the colony and distributed.

Finally, the consul states that the use of “rat funnels” has long been compelled whenever large vessels lie at the wharves.

In Sinyang the work of exterminating rats is in charge of a physician who has 12 assistants, which number, however, may be increased in case of emergency. The means employed are trapping, offering rewards, and catching by means of cats. In his report, the consul states that the best results have been secured by trapping. For ridding houses of rats, some use is made of fumigation. It is stated that there is not much danger of rats invading cargo boats, but that in the country rats are present in enormous numbers, and that the problem of their destruction has thus far baffled all attempts at solution. Bounties at the rate of 15 cents per hundred are paid, and in one year the Government expended for this purpose $32,500.

RAT EXTERMINATION IN MADRAS, BOMBAY, AND CALCUTTA, INDIA.

In Madras, Consul N. B. Stewart states there is no legal enactment in effect requiring the destruction of rats, but the Government has done everything in its power to make the public understand the value of such a measure as a preventive against plague. In 1907 a reward of one-half anna, equal to 1 cent, was offered by the city for each large rat killed, and one-fourth anna for each small one. Bounties of one-fourth anna and one-twelfth anna each for the respective varieties of rats were still being continued at the time report was made.

In Bombay, where plague has been endemic since 1896, destruction of rats and examination of all dead rats and evacuation of rat-infected areas are included among the measures taken by the health department in connection with plague operations. In his report Consul E. H. Dennison states that the present antirat campaign in Bombay includes the distribution of poisons, the trapping of rats, and the reward of 1 cent for each live rat, and a half cent for each dead rat, delivered to the health department. He also states that there are no by-laws or acts under which the destruction of rats can be enforced in private houses.

On account of religious opposition, and to teach the people, educational posters signed by the health officer were displayed, containing advice what to do to prevent plague, which in part reads as follows:

1. Beware of rats in your dwelling houses.

2. To harbor rats is to court plague.

3. Rat infection and consequent rat mortality are the indications of the impending plague visitation among human beings.

4. Allow the health department staff to place rat traps in and about your houses to catch rats and take them back.

5. Freedom from plague is in the removal of rats.

6. Inform the health department when dead rats are found in or near your houses.

7. Clear your houses of all materials likely to harbor rats.

The same placard also contains information regarding disinfection to kill fleas, evacuation of infected areas, and inoculations to produce immunity.

In a special report dated January 23 the consul described a new experiment in rat destruction; that is, an intensive effort in the Kamatipura district. The district was divided into divisions and subdivisions in which simultaneously there were distributed for use on a certain day 19,642 poison baits and 2,670 traps. It was stated that as a result hundreds of rats were collected the following morning.

No reference is made to measures taken for the destruction of rats aboard ships in the harbor.

In Calcutta, it is reported by Consul-General W. H. Michael that various methods are resorted to for the extermination of plague, rats, the use of poison being the most general. Rewards have been offered for live and dead rats, and about 11,135 dead rats were produced, but it was found that a considerable portion of these was picked up by conservancy coolies, and the reward for dead rats was therefore discontinued. Of live rats, only 9,447 were produced. After December 1, 1908, the reward was raised to 4 cents, with the result that 49,396 live rats were captured. It is stated, however, that this did not seem to have any appreciable effect upon the rat population.

RAT EXTERMINATION IN YOKOHAMA AND NAGASAKI, JAPAN.

In the Kanagawa Ken, in which Yokohama is located, the following ordinances relating to the extermination of rats have been enacted:

Kanagawa Ken Ordinance No. 64 of 1902 (issued October 8).

Finders of dead rats within the prefecture shall immediately report and deliver same to the nearest police, village, or other authorities in charge. Upon receipt thereof, the police or other authorities shall without delay transmit the same to the police headquarters (Yokohama).

Kanagawa Ken Ordinance No. 45 of 1903 (issued June 26).

Finders of a dead rat or capturers of a live rat shall report and deliver the same within twelve hours to the police, mayor, medical inspector or officer, antiplague committee, or officer in charge of the Hygiene Guild.

Violation of the foregoing shall be punishable either by a fine or detention in jail.

Kanagawa Ken Ordinance No. 63 of 1907 (issued June 8).

Persons who plan or are engaged in the importation of rats from without into the city of Yokohama, or persons who plan to breed rats in the said city, shall be punished by detention in jail or by a fine.

Extract from Kanagawa Ken Ordinance No. 14 of 1907, relating to supervision over storage and warehouses (issued March 6).

ARTICLE 1. The term “storage and warehouses,” hereinafter mentioned, shall mean and include any godown, storage or storehouses, or warehouses, used by storage or warehouse companies, individuals, forwarding agents or express companies, wholesale dealers, works and factories, wherein cotton, cereals, or grains, flour, peanuts, beancake, and other pressed oil cakes, cocoons, feathers, leather, old or waste cotton, old straw, bags, etc., are stored and kept.

ART. 8, sec. 1. Owners of a storage or warehouse shall exercise at least four times a year a rigid and thorough method of house cleaning and rat destruction in the storage or warehouse. The date and time of cleaning shall be reported to the police, to whose satisfaction and approval the cleaning must be carried out.

ART. 8, sec. 2. Owners of a storage or warehouse shall furnish and always keep at each doorway a suitable rat trap, and shall always endeavor to exterminate rats or pursue such method of extermination as may be directed by the police.

In forwarding the above ordinances, Vice-Consul Babbit stated that vessels engaged in foreign trade, when deemed advisable by the harbor authorities, are required to endeavor to exterminate the rats on board by sulphur fumigation or other effective methods, as are also coastwise vessels.

To encourage the extermination of rats, the mayor of Yokohama was authorized by the city council to pay bounties, the rate being 3 sen (1½ cents) each. The vice-consul states that in addition to this purchase price a ticket is given for a lottery, and for each 60,000 rats 156 prizes, amounting to a total of 1,000 yens are given by the city.

In a table giving the number of rats purchased and sent to the hygiene bureau for bacteriological examination, it is seen that for the year ending December 31, 1908, 447,981 were received.

In Nagasaki the municipal council passed an ordinance January 6, 1906, as follows:

1. Rats to be purchased are of two kinds—house and field rats—and they must be either caught or found dead within this city.

2. A bounty of 3 sen (1½ cents) shall be paid for each rat with a ticket, to be cashed on presentation.

3. Such tickets, to be cashed, must be presented at the city office within thirty days from the date of issue.

4. Rats shall be purchased at the city office, police stations, branch police stations, police boxes, or by city officials, who go around for such purpose, by giving a ticket to be cashed upon presentation, provided that distinction must be made between a rat caught and one found dead.

In transmitting a copy of this ordinance Consul G. H. Scidmore stated that it was issued in accordance with the infectious diseases law of Japan, No. 36, of March, 1897, which provides that cities, towns, and villages shall make all necessary arrangements relating to the extermination of rats as may be ordered by the prefectural governors.

He also stated that when the above ordinance was decreed the mayor of Nagasaki issued detailed instructions regarding its enforcement. The ordinance was enforced from the time of its enactment until July 7, 1908, when the city ceased paying bounties; from January 13, 1908, to July 7, 1908, 980.33 yen ($488.20) having been expended, and 30,767 rats having been destroyed.

RAT EXTERMINATION IN LOURENÇO MARQUEZ, EAST AFRICA, AND MADAGASCAR.

In Lourenço Marquez, Consul W. S. Hollis states that a disinfecting barge is maintained, and requisitioned from time to time by vessels, by which means considerable numbers of rats are destroyed.

He also states that the last efforts to destroy rats on shore were made during the plague outbreak in November and December, 1907.

In a circular accompanying Provincial Decree No. 754 of the governor-general, the following relates to the destruction of rats:

1. For the destruction of rats we advise the public to make use of poison paste.

2. These may be obtained by requisition on the municipal chamber and from police stations.

3. The paste furnished shall be divided into portions and distributed in different parts of the dwellings.

In Provincial Decree No. 737, issued December 11, 1907, by the governor-general, it is required that grain and forage warehouses and stables be provided with cement floors, and that ventilators be provided with wire screens sufficiently fine to prevent the access of rats, and that interior doors and salient angles be provided with metallic points to prevent the climbing and entrance of rats.

Footnote CN:

Cases of pest in Lourenço Marquez, official report.

In Provincial Decree No. 48, issued by the governor-general January 30, 1908, it is proposed among other things to establish a permanent service for the capture and bacteriological examination of rodents in the city and its suburbs.

In transmitting the publication containing copies of these decrees the consul stated that by the end of February, 1908, the campaign against rats was relaxed, and since then nothing had been done to continue the work of extermination.

In Tamatave, Madagascar, and other ports of that island no efforts were being made to exterminate rats, and the American consul reported that there were no municipal or colonial laws or regulations directing such action.

RAT EXTERMINATION IN CAPE TOWN, SOUTH AFRICA.

In a report dated January 20, 1909, Dr. A. J. Gregory, medical officer of health for the colony, states that at present no persons are solely employed on rat catching, but the sanitary staff is required to take all possible measures to reduce the rodent population. By the use of bird lime a very large number of rats have from time to time been destroyed. Doctor Gregory also refers to experiments made to determine the value of tar and funnels placed on ropes to prevent the access of rats to ships. The experiments were made to simulate actual conditions that would prevail at ships lying at docks. It was found that thickly coating a rope with fresh tar had not the slightest deterrent effect on rats passing along. Funnels of a less diameter than 20 inches were equally unsuccessful, and it was thought the experiments proved the fallacy of trusting to tarred ropes or to disks of a workable diameter being able to prevent rats from migrating in either direction between shipping and shore.

RAT EXTERMINATION IN ALEXANDRIA AND CAIRO, EGYPT.

In Alexandria, Consul D. R. Burch stated that measures for the extermination of rats were practiced; that the cost of disinfection was defrayed by the municipality, which also supplied rat traps and poison.

In Cairo rat destruction was being practiced, but it was stated that the results could not be described as encouraging.

EXTERMINATION OF RATS IN THE PORT OF CONSTANTINOPLE.

Consul-General E. H. Ozmun, at Constantinople, states that while no special measures have been taken to exterminate rats in that city, the sanitary administration of the Ottoman Empire has provided measures for the destruction of rats and mice on all vessels arriving from places contaminated with plague, and he has furnished the following copy of instructions concerning vessels which have or have not undergone disinfection in view of destroying rats and mice on board:

ARTICLE 1. Vessels coming from places contaminated with plague and which have not been disinfected either in the port of departure or in an intermediary port during voyage, for the destruction of rats and mice on board, according to the regulations of the superior council of health, shall undergo their disinfection in the lazaretto while finishing their quarantine.

ART. 2. Vessels coming from places contaminated with plague provided with a certificate stating that the aforementioned disinfection has been undergone may, after their admission, work in the port but without landing on the quay.

ART. 3. Vessels proceeding from an uncontaminated Ottoman or foreign port and which are provided with the certificate mentioned in article 2 shall be free to moor at the quay if it is proved that the vessel has been disinfected within a period of forty days; if not, the vessel will operate in the port or at anchor.

Vessels in a similar case not provided with this certificate but which can prove by the journal of the vessel that they have not sailed within a period of four months to a contaminated port shall be authorized to moor at the quay.

ART. 4. Vessels mooring at the quay must be at a distance of from 1 to 2 meters (39⅓ inches to 78¾ inches) maximum. During night they must draw up the gangways and ladders, and must leave no towline suspended without protecting it with funnels, brush wood, etc.

The vessels working in the harbor must also protect their towlines in the same manner.

It is prohibited for lighters and boats to remain attached to these vessels during the night outside of the time for working.

ART. 5. The above-mentioned vessels, mooring at the quay and on the way to an Ottoman port, shall be required after having finished the loading and discharging of cargo, to pass through the disinfection prescribed by article 1 if their certificate of disinfection mentioned by article 3 is found to be out of date, and also as long as the city of Constantinople shall be considered as contaminated.

ART. 6. Vessels coming from uncontaminated quarters, although not under any restraint, are free to go to any lazaretto in the Empire and ask to be disinfected according to article 1; the latter will work without delay so as to prevent loss of time as much as possible.

ART. 7. The expenses of disinfection are to be paid by the vessels disinfected.

ART. 8. Captains, doctors, or any officers of vessels are expected to furnish the sanitary authorities with all information asked for relating to the presence of rats and mice on board the vessel.

RAT EXTERMINATION IN RUSSIAN PORTS.

In Vladivostok, according to Consul Lester Maynard, the only efforts to exterminate rats were made by the commissary department of the army. Poisons, which had for their active principle caustic lime, were distributed but were not entirely satisfactory, as the baits were not sufficiently tempting food.

The keeping of cats had been recommended as the best method of exterminating rodents, and it had been suggested that skunks, weasels, and similar animals should not be killed, as they are the best destroyers of rats and mice.

In Riga and Libau there were no laws and regulations prescribing a systematic extermination of rats. The consul reported that only in case of plague did the sanitary authorities order a thorough destruction of rats not only on ships but also in warehouses and private dwellings. The steamship companies, however, were said to employ rat poison on their vessels, and, in addition, the ships were thoroughly disinfected by means of sulphur fumes several times a year.

In Odessa it was reported by Consul J. H. Grout that the public health officers of the port had been fully alive to the importance of exterminating rats in order to prevent plague. In 1901 a systematic extermination of rats on board vessels had been inaugurated, and in 1902 this practice was extended to include all vessels leaving the port. The agent used in this process was the burning of sulphur in specially designed iron containers. In 1902, 2,054 rats were killed in 346 vessels. In 1903, 1,038 rats were killed in 68 vessels. In 1904, 17,074 were killed in 168 vessels. In 1905, 512 rats were killed in 166 vessels. In 1906, 553 rats were killed in 188 vessels. In 1907, 1,887 rats were killed in 135 vessels; and in 1908, 1,138 rats were killed in 97 vessels.

In St. Petersburg and vicinity no consistent effort, according to the consul, had been made to exterminate rats, but at Cronstadt the port authorities had experimented with ratin.

DESTRUCTION OF RATS IN TRIESTE, AUSTRIA.

All vessels arriving at Trieste from plague-infected countries on board of which rats appeared in abnormal numbers were disinfected with sulphur in accordance with rules of the Paris convention of 1903. Consul G. M. Hotschick stated that it was a rule, whether rats were numerous or not, to disinfect every vessel every six months so as to exterminate rats on board. An exception was made in the case of the Austrian Lloyd steamships plying between Trieste and the Far East, these vessels being disinfected by the Clayton apparatus. All attempts to destroy rats along the port shore had proven fruitless, according to the consul, but in custom warehouses cats were kept, thus limiting the number of rats.

The rules applying to Trieste extended to all the ports of Austria.

DESTRUCTION OF RATS IN GENOA, ITALY.

The methods employed at Genoa for the extermination of rats found on ships were those prescribed by the ministry of the interior at Rome in accordance with the Sanitary Convention of Paris.

As stated by Consul-General J. A. Smith, the regulations place all ships arriving from plague-infected ports into three categories, as follows: Infected, suspected, and noninfected. On ships coming under the first two headings all rats must be destroyed previous to the ship being allowed to pass quarantine. Noninfected ships were subject to the same regulations only in case of an unusual mortality among rats aboard, or in case of an excessive number of them being found on board on arrival, which, in the opinion of the port medical officer, required their destruction. Sulphur was used as the agent of destruction, the gas being generated in a special apparatus. This apparatus had been installed in the ports of Naples, Genoa, Messina, Brindisi, Venice, and Asinara.

Further regulations of the ministry provided for the means to be employed in preventing rats from reaching shore.

RAT DESTRUCTION IN BARCELONA, SPAIN.

In Barcelona Vice-Consul-General Wm. Dawson, Jr., reported that the officials in charge of public health measures attached no really great importance to the destruction of rats as an effective means of preventing the spread of plague. Several attempts, however, had been made to kill rats, which invade Barcelona to an enormous extent. In his report the vice-consul further stated that bacterial cultures known as Tifus ratoso, and supposed to have given excellent results in Formosa, had been tried without appreciable results on wild rats. He further stated that wheat boiled in a 5 per cent solution of corrosive sublimate, dried in the air, and spread in sewers and other places, had proved the most effective means of killing a few thousand of them, but this practice had not been carried out to any great extent nor for any length of time.

RAT DESTRUCTION AT FRENCH PORTS.

In Marseille the following was the practice as reported by the director of the maritime health service at that port and forwarded by Consul-General H. L. Washington:

The obligatory destruction of rats in all French ports is enforced by virtue of a decree dated May 4, 1906. This applies: (1) To all vessels arriving from a port regarded as contaminated by plague or having only touched at such port. (2) To all vessels having received in transshipment—that is to say, from ship to ship—merchandise originating in a country deemed contaminated by plague. The destruction of these animals is carried out exclusively by means of apparatus whose efficacy has been recognized by the Superior Council of Hygiene of France.

The devices employed at Marseille are:

(1) The “Marot,” adopted June 19, 1905. This apparatus utilizes liquid sulphurous anhydrite, which is slackened, diluted in the air, and subjected or not to the action of the electric spark. The gas is introduced into the vessel by means of a ventilator at a rate of from 25 to 30 meters per minute (82.02 to 98.42 feet).

(2) The “Gauthier-Deglos,” adopted February 18, 1907. This method requires the combustion in an oven of a mixture of sulphur and coal dust. A ventilator withdraws air from the vessel and causes it to pass over the mixture in combustion; the gas thus produced is cooled and then introduced into the vessel. A third device, known as the “Clayton,” in use in some of the French ports, also operates from time to time in Marseille on such vessels as are provided with it, but it does not exist in the port itself. The principle of this device is based upon the combustion of sulphur, its transformation into sulphurous sulphuric gas, the cooling of the gases leaving the oven, aspiration of the exterior air or the air in the holds of vessels, and introduction into the holds by means of a powerful ventilator.

With all three systems, the ships’ holds are opened only after they have been in operation for three hours.

In Bordeaux, according to the consul, contracts had been entered into between the Government and a private individual for the extermination of rats on all ships coming from plague-infected ports, the apparatus employed being that in use at Marseille.

In Havre the extermination of rats on vessels from plague-infected ports was reported by Consul A. Gaulin as being systematically carried out in accordance with a ministerial decree of May 4, 1906, which is as follows:

ARTICLE 1.—The destruction of rats, or “deratization,” effected exclusively by means of apparatus the efficiency of which has been recognized by the Superior Council of Public Hygiene of France, is obligatory for admission into French ports:

1. Of every ship coming from or having called at a port considered as being contaminated with plague.

2. Of every vessel having taken in transshipment—that is to say, from one vessel to the other—more than 50 tons of merchandise coming directly from a country considered as being contaminated by the plague.

The above provisions are applicable to vessels having already discharged a part of their cargo in one or several foreign ports.

ART. 2.—May be exempt from deratization:

1. Vessels which only land passengers in French ports without docking and which sojourn only several hours.

2. Vessels making a call of less than twelve hours and discharging less than 500 tons of merchandise, on condition that the surveillance of discharging be accomplished during the day exclusively, the ship being moored away from the quays, and the hawsers provided with rat guards.

3. Steamships which shall not have called at any port considered as being contaminated by the plague for sixty days since their departure from the last contaminated port, and on board of which there shall have been observed nothing of a suspicious sanitary nature.

4. Vessels which, having called at a port considered as being contaminated by the plague, will prove that they neither berthed alongside the quay or landing stages, nor embarked merchandise.

5. Vessels which have undergone the process of deratization in a foreign port subsequent to their departure from the last port considered as being contaminated. It must be proven, in this case, that nothing of a suspicious sanitary nature has taken place on board during the voyage, and that the deratization has been effected with the same apparatus and the same guarantees as in France. The captain of the vessel shall deliver as proof to the sanitary authorities a certificate mentioning the apparatus employed, the conditions under which the operation was effected, the verifications made, etc., and a certificate viséed by a French consular officer.

6. Vessels whose status is that indicated in paragraph 2 of article 1, on condition that the merchandise has been transshipped from a vessel which has been deratized under the conditions prescribed in the preceding paragraph, and if such merchandise is accompanied by a certificate of deratization provided for in said paragraph.

ART. 3.—Shall be considered as merchandise, for the application of the present decree, all products embarked, figuring or not figuring on the manifest, the only exception being coal embarked for the needs of the ship without touching the quay.

ART. 4.—Deratization may be effected during the voyage by any French ship having a surgeon, and one of the machines prescribed by article 1.

The sanitary official at the port of arrival shall determine, upon examining the documents presented and the proofs furnished, the conditions under which the operation has been effected, and he may exact a total or partial renewal of the same.

The same provisions are applicable to foreign vessels, by virtue of reciprocity, on the twofold condition that the sanitary officials of the one (nation) enjoy the same standing as French sanitary officials, and that the apparatus used are the same as those mentioned in article 1.

ART. 5.—In ports, the deratization is effected before the unloading of the ship.

The operation comprises the holds, bunkers, storerooms, crew’s quarters, emigrants’ quarters or compartments for third and fourth class passengers, and, in general, all interior compartments of the ship.

The officers’ cabins, and those of first and second class passengers, as well as the dining rooms, and saloons which are provided for them, are not subjected to deratization except in cases where the sanitary official judges it necessary—notably when the ship is suspected of being or is infected by plague, when it has been observed that the malady exists among the rats on board, or when there has been a death from unusual causes.

ART. 6.—The apparatus to be employed for the deratization, by virtue of article 1, are placed at the disposal of the owners or agents, according to the conditions approved by the sanitary authority.

Ports possessing one of these machines are alone open to vessels coming from countries considered as being contaminated by plague.

The operations are effected under the permanent supervision of the sanitary authority and with the least possible delay.

ART. 7.—The expenses of deratization are borne by the owners, in conformity with the provisions of article 94 (last paragraph) of the decree of January 4, 1896. No sanitary tax is due, in consequence, for the operation.

ART. 8.—The expenses considered in article 7 are based on the gross tonnage of the ship, if the deratization comprises all its parts, and on the cubic capacity of the parts deratized, if the operation is partial. The cubic capacity is determined by and from the plans of the ship, without allowing for the space actually occupied by merchandise.

ART. 9.—A certificate setting forth the conditions under which the operation has been effected is delivered to the captain or owners by the sanitary authority.

ART. 10.—Ships which are not necessarily subject to the requirements of deratization may, upon their request, be subjected to this operation upon their departure, as on their arrival, either with full or empty holds, and obtain, in consequence, the delivery of the certificate mentioned in article 9. Every facility should be accorded them for this purpose.

ART. 11.—Violations of the provisions of the present decree are punishable by the penalties set forth in article 14 of the law of March 3, 1822, independently of the measures taken for the isolation or other measures to which ships are subjected by reason of their origin or the sanitary condition on board at the time of arrival.

ART. 12.—Are annulled, the decree of September 21, 1903, and the provisions of the decree of September 23, 1900, which would be at variance with the second paragraph of article 6 above cited.

ART. 13.—The minister of the interior is charged with the execution of the present decree, which shall be published in the Official Journal, inserted in the Bulletin of Laws, and posted in the ports.

DESTRUCTION OF RATS IN GERMAN PORTS.

In Hamburg, according to Consul-General R. P. Skinner, stationed at that port, persistent efforts were being made to exterminate rats not only on board ship but in the city itself, and he reported the following method of procedure:

Upon the arrival of every vessel an inspecting officer employed by the board of health boards the same to inquire whether, during the voyage, rats have died in exceptionally large numbers. While in port the vessel is visited almost daily by inspectors, who search for dead rats, particularly in the holds. On vessels from such ports whence plague-infected rats have been brought to Hamburg repeatedly an officer of the board of health is posted on board constantly to watch the discharging of the cargo. All dead rats found are immediately delivered to the Hygienic Institute; and if the latter’s bacteriological examinations give reason to suspect plague, the discharging is immediately discontinued and communication with the shore interrupted. The vessel’s crew and discharging gangs are placed under medical observation for a period of five days, the cargo compartments are treated with generator gas, so as to exterminate all rats, and, after the quarantine has been discontinued and the cargo discharged, all compartments are carefully disinfected. For the purpose of treating infected ships by means of generator gas the Hamburg government owns a special disinfection ship, called the Desinfektor, which will be described later.

In order to exterminate rats on ships frequenting the port of Hamburg the master of every vessel arriving here receives the following instructions from a representative of the health officer of the port:

He shall cause rat poison to be laid and fumigate holds by means of sulphur and charcoal as soon as the cargo has been discharged, not less than 10 kilos (22 pounds) of sulphur and 20 kilos (44 pounds) of charcoal to be used for a room of 1,000 cubic meters (1,308 cubic yards). Such rooms must be kept closed at least ten hours. On ships arriving from ports infected with plague, rat poison is laid, free of charge, immediately upon arrival, by an employee of the municipal disinfection establishment, at all places within reach. On all other ships the laying of rat poison is done by private persons whose charges are payable by the vessel’s master or owner.

The disinfectors employed by the State of Hamburg use principally a rat poison called “Rattengiftspeise,” consisting chiefly of phosphorus and squills. Private rat killers may choose any other material, but from time to time samples of such poisons as are laid out on ships are taken by order of the harbor surgeon, and rats kept in the public laboratories are fed with them, to enable a control as to the effectiveness of the poison.

Under special circumstances the harbor surgeon is authorized to waive the requirement of fumigation.

Killed rats are not permitted to be thrown overboard, but must be delivered to the nearest police station, which causes their cremation.

On river barges rat poison is laid by official disinfectors every three months.

Finally there is rat poison laid, from time to time, in warehouses, cargo sheds, and trade establishments in the harbor, partly by official disinfectors and partly by private rat killers, which is regularly controlled by the harbor surgeon, a special officer of his department being engaged for such purpose.

The ship called the Desinfektor, owned by the government of Hamburg for the purpose of disinfecting ships arriving from infected ports and for the extermination of plague infected rats, is a steamer equipped with a generator gas apparatus and other disinfecting facilities. The method of using generator gas has been chosen for reasons which are described in a booklet issued some time ago by the local board of health on this subject.

In respect to the extermination of rats in Hamburg, aside from the system adopted for ships and in the harbor, the consul-general states that efforts to this end are being successfully carried out by official disinfectors by order of the board of health, and he refers to the procedures as follows:

If it becomes known to the board of health that in any locality or group of buildings there are rats in large quantities, rat poison is immediately laid. For such purpose the above-mentioned Jungclaussen’s preparation is almost exclusively used. The several local citizens’ associations (Bürgervereine), at the meetings of which all topics of interest are discussed, contribute largely to the bringing to the knowledge of the proper authorities of all matters a remedy of which is, in public interest, considered necessary, among them rat and mice nuisances in the several districts of the city. Of late the board of health has also begun to lay rat poison in houses in the old parts of the city, employing the house-to-house method, and rat poison is laid, from time to time in sewers and other underground canals where rats usually congregate in large numbers.

As the laying of rat poison at or in the vicinity of places where domestic animals are kept is dangerous to the latter, the Hamburg board of health has only shortly ago caused a small gas generator to be constructed, similar to that on the Desinfektor. The apparatus can easily be removed from one place to another, and is chiefly to be used on yards or unimproved lots, public parks, zoölogical gardens, etc., where rats live under the ground. In fumigating such a rat nest, all holes leading out of it are closed with earth, except two. The hose of the gas apparatus is introduced into one of the holes and gas insufflated. The majority of rats in the hole are dead before being able to reach the fresh air. Those succeeding in doing so, by getting out of the one open hole, are so dizzy that they can easily be killed with a club. Only a few experiments have so far been made with this apparatus, but the same promises good success.

In Bremen, according to the consul, all disinfection of vessels and their cargoes was done with sulphur dioxide by means of a Clayton apparatus, and vessels equipped with this apparatus, and those having physicians aboard, had the advantage of being able to start disinfection twenty-four hours before arrival at port, this process having been recognized as sufficient compliance with the quarantine laws of Germany.

MEASURES AGAINST RATS AT THE PORT OF ROTTERDAM.

In the report from Consul-General S. Listoe it was stated that the extermination of rats had not been officially undertaken by the authorities of Rotterdam, either in the port or aboard incoming ships. The question had been investigated, however, and the harbor master had strongly advised the installation of a fumigating machine, which would be installed on one of the numerous river police boats. Ship owners had, for their own protection, caused their ships to be occasionally fumigated, and two of the well-known lines had fitted out some of their steamers with fumigating apparatus.

DESTRUCTION OF RATS AT ANTWERP, BELGIUM.

Consul-General H. W. Diedrich stated that no official action had been taken in the port of Antwerp for the extermination of rats, but that every vessel entering the port had to pass the sanitary station at Doel, and there was authority to hold up any suspected vessel and to insist on fumigation for the destruction of rats.

DESTRUCTION OF RATS IN DENMARK.

As a result of the agitation started in 1898, the following law was passed and signed by the King of Denmark on March 22, 1907:

1. When an association constituted for the purpose of effecting the systematic destruction of rats has proved to the satisfaction of the minister of the interior that it is in a position to expend on the furtherance of its objects, within a period of three years, a sum of not less than 10,000 kroner per annum, it shall become incumbent upon each local authority to make suitable arrangements at the expense of the local funds, and commencing with a date to be made known hereafter by the minister of the interior, for the reception and the destruction of all rats killed within the district of such authority and delivered up to such authority.

For each rat delivered up each local authority shall pay a premium, for the payment of which an annual grant shall be made out of the local funds, which shall be not less than three kroner per each hundred inhabitants within the district of each local authority, according to the then last general census.

The State shall make for a period of three years an annual grant of 30,000 kroner, of which one-third may be expended on scientific experiments with preparations for the extermination of rats, under the control of, and in consultation with, the Royal Veterinary and Agricultural College, while the remainder shall be expended on purchasing preparations for the extermination of rats, which shall be either employed on or in public lands or buildings, or out of which remainder grants may be made to associations toward the purchase of such preparations, in a manner to be defined hereafter by the minister of the interior.

2. Each local authority shall fix the amount of the premium (sec. 1) which shall not, however, be more than 10 oere or less than 5 oere.

Instructions for the collection and destruction of the rats killed will be issued by the minister of the interior.

3. The association cited in section 1 shall submit for the sanction by the minister of the interior at the beginning of each year a plan showing the proposed expenditure, and at the end of each year an account of the money expended by it, together with statistics obtained by it showing the expenditure on premiums made by each local authority.

4. Where the proprietor or occupier of a messuage has participated in the grant to be made by the State (sec. 1), he shall not deliver up, or cause to be delivered up, for the purpose of obtaining a premium or premiums, rats killed within the said messuage, until the expiration of one month from the employment of such preparation for which such grant has been made. Any person acting in contravention of this section shall be liable to a penalty of 100 to 500 kroner.

5. Any person who preserves or breeds rats or imports rats from abroad, in order to obtain premiums or enable another person to obtain them, shall be liable to a penalty of 100 to 500 kroner, unless he is liable to a higher penalty under the common law. A person who shall deliver up rats knowing them to have been preserved, bred, or imported for the purpose of obtaining a premium shall be liable to the same penalties.

All proceedings under this act shall be taken in a public police court, the fines to go to the special funds provided by this act, or where such fund does not exist, to the public funds of such local authority.

Any person delivering up rats to any other local authority than to that within the district of which they have been caught shall be liable to a penalty not exceeding 100 kroner.

This act shall come into operation on a date to be fixed hereafter by the minister of the interior and remain in operation for three years.

In the session of the Riksdag immediately preceding the expiration of this law a vote shall be taken for the renewal or revision of this law.

The Government is authorized by royal rescript to make such alterations in the operations of this law within the Faroe Islands as may be considered most suitable, having regard to the special conditions obtaining within those islands.

Following the enactment of this law, there was issued by the ministry of the interior May 1, 1907, a circular to the local authorities on the subject.

CIRCULAR TO THE LOCAL AUTHORITIES.

Whereas the Association for the Authorized Extermination of Rats has proved to the satisfaction of the ministry of the interior that it is in a position to expend on the furtherance of its objects not less than 10,000 kroner within a period of three years, it is hereby requested, in pursuance of act No. 59, of the 22d March, 1907 (see public notice dated this day), and commencing with the 1st day of July of this year each local authority shall at its own expense take all such measures as may be necessary for the reception and destruction of all rats killed within the district of such authority and delivered up to it. For the purpose of paying a premium for each rat delivered up each local authority shall out of the common funds make an annual grant which shall be not less than 3 kroner for each hundred inhabitants, according to the then last general census, should the amount required for the payment of premiums make such grant necessary. It shall be left to each local authority to decide whether further grants shall be made toward this purpose. The premium to be paid for each rat delivered up shall not be more than 10 oere or less than 5 oere, and shall be fixed by each local authority which shall give due and sufficient notice both of the date fixed for the commencement of the operations of the law and the premium to be paid. As far as possible, a uniform rate of payment by premium shall be fixed by local authorities within the same county. Rats may not be delivered up to any local authority but to that within the district of which they have been caught; any person acting in contravention (par. 5 of the aforementioned law) shall be liable to a penalty not exceeding 100 kroner.

The chairman of the councils of the various local authorities are hereby requested to take steps for the discussion and carrying out of the provisions of this law.

If the grant made by any local authority for the purposes of this law should prove insufficient for the payment of premiums on all rats delivered up, such authority may apply to the Association for the Authorized Extermination of Rats, Colbjornsengade 14, Copenhagen B, for a subsidy, this association having undertaken to organize the obtaining of voluntary subscriptions for the carrying out of the purposes of this act.

The said association is further prepared, at the request of local authorities, to render expert assistance in commencing and carrying through operations under this act.

For the collection and destruction of rats killed the ministry of the interior issues the following instructions:

A.—THE LARGER TOWNS.

Collecting depots.—The local authorities shall provide a sufficient number of places suitable for collecting depots. Such depots must not be within any place where food or clothing is made or offered for sale. Fire brigade stations are considered most suitable for collecting depots.

The collecting may suitably be done in the manner that for each depot a number of receptacles are provided, made of galvanized iron and furnished with a tight-fitting lid. Into these receptacles the rats are to be thrown after their tails have been cut off. The tails are to be kept in a separate tin box. All receptacles and boxes are to be collected daily and to be replaced by empty receptacles. The full receptacles are to be taken to the place where the destruction of the rats is effected.

Further advice on the purchase of such receptacles and the apparatus for cutting off their tails will be given by the Association for the Authorized Extermination of Rats at the request of a local authority.

The destruction may be effected either by cremating the dead rats—for instance, at the municipal gas works—or by burying the carcasses in the open, at a sufficient distance from the town, unless this course is prohibited by local sanitary considerations. It is recommended that the local authority act in this manner always with the local health committee.

B.—THE SMALLER TOWNS.

Instead of opening a fixed depot, it would appear more suitable in the smaller towns to provide a collecting cart. Any horse-drawn vehicle would serve the purpose as long at it is furnished with a fixed apparatus for cutting off the tails and a receptacle of galvanized iron for receiving the carcasses of the rats. The vehicle should also be fitted with a bell, to announce the arrival and presence of the collecting cart.

The destruction of the carcasses is to be effected in the manner described under A.

C.—THE VILLAGES.

The authorities in the villages shall appoint a suitable person to receive the rats delivered up, for which work he shall be paid an adequate remuneration. Such persons must be supplied with an apparatus for cutting off the tails of rats handed in. After the tails have been cut off, the rats may be buried in a suitable place without delay. It is most undesirable that any person engaged in the carrying of milk or other foodstuffs be asked to convey rats to the persons appointed to receive them. Villages in close proximity to towns are advised to make arrangements for the cremation of the rats at the municipal gas works.

In the case of villages whose buildings approximate those of a town it is recommended that the regulations given for towns are adopted.

Respecting the payment of the premiums it is recommended that the person in charge of a collecting depot or otherwise appointed to receive rats is supplied with a fixed amount of petty cash, out of which he pays the premium for each rat delivered up. The tails cut from the rats serve as a receipt for the payment made, so that the total amount of tails will be a discharge for the total amount of petty cash received and paid out in premiums.

In order to prevent abuse it is particularly requested that the local authorities take care that the rat tails are destroyed in an efficient manner as soon as they have served the purpose of control and checking.

For the purpose of keeping satisfactory accounts the Association for the Authorized Extermination of Rats has on sale specially arranged account books which are recommended by the ministry of the interior.

As in accordance with paragraph 3 of the law of 22d March, 1907, it is the duty of the Association for the Authorized Extermination of Rats to submit to the ministry of the interior a report on the money expended in the whole of the kingdom on such premiums, the local authorities are hereby desired to make a quarterly return to the aforementioned association on the number of rats killed within the district of each authority in each month of the quarter covered by such return and on the money paid out for premiums. Forms for such returns will be supplied by the association.

Any associations which in accordance with terms of paragraph 1 of the law of 22d March, 1907, desire to participate in the grant made by the State for the purpose of purchasing preparations for the extermination of rats (ratin, etc.) must send a request to that effect to the minister of the interior, together with a statement showing the approximate cost of the proposed campaign and the amount at the disposal of the association for that purpose. As this law is essentially of an experimental character, the requests of all such associations will be treated as preferential, which show that the proposed extermination may be easily and successfully effected (as, for instance, on small islands).

A number of copies of this circular will be forwarded to each local authority.

DESTRUCTION OF RATS IN SWEDISH PORTS.

Consul W. H. Robertson at Gothenburg, Sweden, quoted the city physician to the effect that “upon the appearance of plague in Great Britain the city council decided in April and November, 1901, to make an appropriation of $2,680 for an attempt to reduce the number of rats within the community.” These attempts were continued during the period May, 1901, to September, 1902, 2.68 cents being paid for each rat caught. Any unusual mortality among rats on board a vessel coming from a plague-infected port was being dealt with in accordance with a royal proclamation of June 16, 1905.

In Malmo, according to the consular agent, the authorities during the past seven years had given a premium for every rat killed during the first five years, 2.68 cents for each rat, but during the past two years only half of that amount.

DESTRUCTION OF RATS IN ENGLISH PORTS.

The Local Government Board has issued regulations for the prevention of plague and certain other diseases. One of these regulations is as follows:

The master of a ship which by reason of plague is an infected ship, or a suspected ship, or which has come from, or has during the voyage called at, a port infected with plague, or in which there are rats infected with plague, or in which there is or has been during the voyage an unusual mortality among rats, shall, under the direction and to the satisfaction of the medical officer of health, take all such precautions or employ all such means for effectually stopping the access of rats from the ship to the shore as in the opinion of the medical officer of health are measures reasonably necessary for the prevention of danger arising to public health from the ship.

In accordance with this regulation, notice was given in a circular issued by the medical officer of health of the port of London of the precautions necessary for stopping the access of rats from ship to shore in that port. These precautions were outlined as follows:

1. All ropes and mooring tackle for securing the vessel either to the shore or mooring buoys shall be fitted with metal brushes, funnels, or other effective guards, the portions of such ropes and mooring tackle leading from the vessel to a distance from the vessel’s side of at least 4 feet shall be coated each night with fresh tar. Ropes may, if desired, be protected by a covering of canvas or yarns before tarring.

2. When not engaged in discharging cargo, one gangway only shall be permitted to afford means of communication between the ship and the shore.

3. The end of the gangway near the ship shall be whitened for a length of 10 feet, and the watchman shall keep the gangway pulled inboard after sunset, or it shall be guarded in some approved manner.

4. When alongside the quay, the ports on the side of the vessel nearest the quay shall be kept closed after sunset.

5. All empty cases and barrels, especially those from the storerooms, shall be examined before being landed, to insure that no rats are contained therein.

6. It is recommended that all possible means be adopted for catching and destroying rats, both on the voyage and during the stay of the vessel in port. Any rats so caught shall be killed, then placed in a bucket of strong disinfecting solution, and afterwards burnt in the ship’s furnace.

7. No rats, alive or dead, are to be removed from the ship without my permission in writing.

In London, the practice of destroying rats on the docks had been systematically carried out by the dock companies at their own expense and under the supervision of the port sanitary authority. Vice-consul Richard Westacott reported that the destruction of rats on vessels was provided for by regulation whenever the medical officer of health was satisfied that such precaution against the introduction of the spread of plague was necessary.

In Liverpool, Consul J. L. Griffiths stated that earnest endeavors were made to capture rats by professional rat catchers. On infected or suspected ships, special precautions were taken to prevent the escape to the shore of rodents. On noninfected or nonsuspected ships the medical officer of health might also require the destruction of rats, and in this case the expense was borne by the sanitary authority. It is evident, therefore, that the precautions taken are in accordance with the provisions of the International Sanitary Convention of Paris.

It was the practice, at the time the consul sent his dispatch, to maintain strict surveillance over vessels likely to develop plague aboard until after the period of incubation had been passed.

In Southampton, according to Consul A. W. Swalm, a competent man was employed by the dock authorities whose sole duty was to wage war on rats. In addition, the night watchmen on all vessels were required to perform the additional duty of trapping rats. The usual precautions to prevent the passage of rats from ship to shore were also observed.

MEASURES AGAINST RATS AT AUSTRALIAN PORTS.

The following are the regulations issued under the quarantine act of 1908 by the commonwealth of Australia relating to the ingress to and egress from vessels of rats and mice; the destruction of rats, mice, and other vermin; and precautions against the introduction of vermin from plague-infested places.

136. (1) The master or owner of every vessel shall—

(a) Effectively obstruct—against the migration of rats—by means of stout wire netting, all pipes, ports, cabin scuttles, and other openings or holes in the side of the vessel next to the wharf, and also when cargo is being discharged into lighters, in the side next to the lighters, and keep them so obstructed while the vessel is alongside the wharf or lighters;

(b) Prevent any organic refuse, galley scraps and waste from being discharged into the waters or on the wharfs of any port.

(2) The master or owner of any vessel arriving in any port in Australia from any place proclaimed infected with plague, or as a place from or through which plague may be brought or carried, under