SECTION I. Introduction

INTRODUCTION

“We have also parks and enclosures of all sorts, of beasts and birds; which we use not only for view and rareness, but likewise for dissections and trials, that thereby we may take light what may be wrought upon the body of man.”

The purpose of a menagerie under the auspices of a zoological society can scarcely be put into better words than those found in this quotation from Sir Francis Bacon’s New Atlantis. Apt as this description of the mythical island’s collection may be, it is but a reflection of the teachings of Plato’s original legend of a perfected community, and the practical applications of these teachings by Aristotle in his Anatomy and Physiology of Animals. The history of human study shows a constant investigation of lower forms of life, ever broadening in its scope, ever more satisfying in its explanation of biologic problems and ever increasing in value from an economic standpoint.

If, however, all animals are to be subjected to “dissections and trials” there inevitably will come under observation many specimens presenting variations from the accepted mean or standard or even from an average for their kind and therefore approaching what may be called pathological.

The desire to explain the abnormal has had the effect, during the half century since Virchow defined cellular pathology and Darwin systematized the world’s knowledge of comparative biology, of directing attention to comparative pathology and of stimulating the study of veterinary medicine. Moreover in the past twenty-five years much work has been done and many isolated publications have appeared upon the diseases of wild animals, notably Bland-Sutton’s work, Evolution and Disease (1895), a thoroughly scientific and most charmingly written book, but rather elementary in its approach of the subject of pathology, and Wood Hutchinson’s Diseases of Animals, a more or less popularly presented treatise. I am unaware, however, of any systematic monograph upon the subject wherein we may find data showing the character of pathology in the various animal groups or the incidence of the various lesions. The reports of some zoological gardens contain the result of medical and pathological data collected for the report period. The publication of greatest merit and value is that from the Zoological Society of London, whose huge collection studied by a large official personnel makes it possible to present valuable data. The New York Zoological Park uses its material in a similar manner and has been able to explain some of the knotty problems so frequently met in wild animal collections.

Here at Philadelphia it has been our practice now for twenty years to perform an autopsy upon every mammal and bird that dies, and upon all of the large or important reptiles. There is no aquarium connected with the Garden. The office of the society keeps a record of the arrival and a general description of every animal so that a brief history of the specimen is usually available. The keepers are required to observe their charges regularly and closely and to report any abnormalities to the officials of the Garden. Somewhat detailed discussions upon signs of sickness will be given at appropriate places, where also a few remarks upon treatment will be included, but as this work is not intended to be a treatise on therapy and since this subject does not differ from that referable to domesticated animals, little space will be devoted thereto. Upon death a complete autopsy is performed and the findings are recorded upon a printed form from which, when the histological, bacteriological and parasitological studies have been completed, a set of cross index catalogue cards are typed; these are divided into the principal diagnoses and determinations. The report of the Zoological Society, appearing at the end of their fiscal year, February 28th, contains a résumé of the observations for the year, together with notes of interesting cases and experimental work.

There have accumulated the records of nearly six thousand autopsies and upon them as a basis has been founded the following report of the incidence and nature of pathological manifestations in the various animal groups, using also as additional data, published reports from other gardens. The book might be described as a collection of our studies, parts of which have appeared as separate articles, but most of which are entirely new, put together with as much connection as the subject matter will permit. The zoological and pathological literature has been consulted very extensively, but except for the reports of zoological societies and the publications of special students, it usually represents isolated notes by travellers and veterinarians so that many articles may have been overlooked. Therefore no claim of perfect completeness of reference is made, the statements resting chiefly upon our own records. The subject will be approached from the standpoint of description and incidence, but it is inevitable that comparisons and contrasts must be noted.

Into the realm of evolution I shall not venture because I appreciate a lack of adequate preparation for such an attempt, and because, even if such were not the case, the material at hand is lacking in data upon fishes, many kinds of reptiles and invertebrates.

A direct and practicable application of these data will be in the direction of explaining some of the pathological states in domestic animals and man. There are indeed many disease entities or syndromes in these groups for which no useful hypothesis has been advanced, while for others a partial explanation has been offered, usually, however, inadequate wherewith to form the basis of rational prevention or therapy. Thus, for example, essential emphysema seems to be limited to the animals of civilization; on the other hand, the anatomical basis of exophthalmic goitre may be seen throughout nearly the whole animal kingdom yet the clinical phenomena belong characteristically to man, and are occasionally seen atypically in the dog. While it may be impossible to give a complete comparative anatomy and physiology for each of the pathological states, the attempt will be made to treat all subjects analogically through the zoological orders.

The experimental pathologist may find the records of the Garden useful in his work. For example, he can know that rodents are not prominent among the orders showing spontaneous arteriosclerosis, but that nephritis occurs among them in about a quarter of natural deaths; or he may learn that the Primates have a good cardiac reserve while the Marsupialia have not. Too often experimental work is not based upon facts including natural probabilities.

A collection of pathological data such as is presented in the following pages may be of assistance to veterinarians and managers of zoological gardens in the diagnosis of sickness in animals, both wild and domesticated. We do not presume to offer a system of veterinary medicine, but it is possible to introduce certain objective findings of practical hygienic and therapeutic value. Such observations are, however, limited and in our experience at the Philadelphia Garden the diagnosis of disease in a wild animal, excepting of course those which are perfectly self-evident, is more often speculation and conjecture than at all well grounded. It is not uncommon for animals to come to autopsy presenting a perfect galaxy of abnormalities, yet the closest antemortem observation failed to reveal unusual conduct or appearance. On the other hand specimens are frequently opened whose organs fail to contain any lesions discoverable even by careful study. Dr. Henry Chapman, sometime prosector to the Society, once made a remark in this connection—“Why do they die or how can they live so long.” Space is given to this phase of the observation of wild animals in order to emphasize the difficulties of interpreting their conditions, but of course it should be understood that certain data of value may be gained by close attention to the details of their normal behavior and to changes which occur indicating that something is wrong.

The naturalist and the trained animal keeper are, in our opinion, better judges of a wild animal’s condition than is the veterinarian, unless he be at the same time a zoologist and have long experience with a menagerie. My own observation of dogs and horses leads me to think that more acumen is needed to interpret the actions of wild animals since they seem to have greater natural reserve, and of course in regard to them there are many more variables since we see fewer specimens of each species than we know familiarly among domestic varieties. The principal objects for observation are, as in veterinary medicine, the eyes, the hair and skin, the mucous surfaces, the droppings, the condition of the abdomen, the appetite and the desire for water. Physical examination is limited to tractable beasts and those which can be caught and handled without danger to the personnel or unusual fright and damage to themselves. In the interpretations of physical signs in tractable animals, such as many ungulates and some monkeys, the experience of the trained veterinarian is of the greatest value, but this fails amongst carnivores and birds. It might be said that anesthetics could be used for a thorough examination, but this would be undesirable for a seriously sick animal and it is, in our experience, none too safe a procedure although often perfectly practicable. Animals do not like to be molested much as they may seem to enjoy attention, and when it is possible it is our practice to avoid handling them.

It might be contended that observations upon diseased states in captive animals would not represent natural developments, in other words, not that which occurs in the wild. Such indeed may be true in regard to the infectious diseases, but since we are imperfectly informed as to the pathology of the wild state, we are obliged to accept and use the best substitute at hand. Moreover it seems perfectly fair to consider as characteristic for an animal or group, the physical and even physiological expressions of morbid agencies as we know them, even though the animals be at the time under conditions not natural to them. It would be perhaps incorrect to say that cirrhosis of the liver occurs in .6 per cent. of animals in the wild as is the case for our autopsies, since incorrect food and infections are potent in its causation; on the other hand, our experience and some few data from naturalists and pathologists make it conceivable that tumors occur to this number in native states. The incidence of tumors in wild rodents is quite well known. Degenerations and fibroses, the result of parasitism, are known to exist throughout the entire animal kingdom. Further to illustrate how pathology is distributed in wild life, Plimmer’s experience with 500 rats (M. decumanus) might be cited. He found the following: Tubercle 3 times, tape worm cysts 10, Tryp. lewisi 49, empyema 2, tumor of jaw from old injury 1, pleuritis and hydrothorax 1. Bacteria were found in 71 rats, 40 times in the lungs, 31 times in the spleen; saccharomyces were found 16 times in the lungs. Dr. W. L. Abbott reports to us personally that he has repeatedly found coiled exproventricular worms in the wild specimens he has collected. Not only are we informed of some isolated and individual pathological states but the existence of epizoötics of communicable disease among wild life is well authenticated. The simple citation of the extermination of deer in one section of Colorado by pleuropneumonia will suffice to illustrate this point. Other examples are, however, interesting. The occurrence of changes in the jaw bone almost certainly those of actinomycosis is reported by Blair, the specimens being shot in the wild and believed never to have been near civilization. The white-tailed deer of the Swan River Valley in Montana, are known to be constant carriers of liver-flukes.

It would seem therefore that it is not unfair to use material gathered from animals under somewhat unnatural conditions as representing the reaction of the zoological orders to pathogenic agencies. Such conclusions must however be made very guardedly, for it is probable that not over ten per cent. of the total number of mammalian and avian species are to be observed in captivity. Because of the number of orders and the great variety of genera included in the present study it is probable nevertheless that the lesions are fairly representative of the whole animal kingdom.

However, the numbers and percentages given should be read to indicate the probabilities and should not be interpreted as implying the mortality relationships since different varieties have differing powers of resistance to the same pathological state. The margin of safety in any given group for one or several different disease entities cannot at present be stated with any degree of precision but this factor is doubtless very great. The work of physiologists suggests that there is a reserve power in the human lung sufficient to sustain life until five- sixths of the functionating organ is useless, and I shall quote a case of an opossum wherein only one-tenth of the respirable surface seemed to have remained; we have repeatedly seen both lungs of a monkey apparently entirely solid. Such physical vital incompatibilities might be exemplified by many other cases, but when one reviews the physiological margin of safety, inexplicable and contradictory instances are equally numerous. I have seen a male deer run a doe against the fence and butt her, without result, whereas in an apparently similar occurrence the animal would be dead in a short time. Numerous instances of slight enteritis of a short stretch of duodenum or ileum have killed, with almost nothing to be found microscopically, and on many occasions we have been chagrined in being unable to discover the cause of death. The capacity of self-healing is a variable one, but seems in direct proportion to the quietness and seclusion possible for the animal and inversely to the chance of bacterial infection.

The effect of captivity has been the subject of much speculation. For the preservation of health it would seem that animals require periods of rest and activity, thorough elimination, possibly a moderate exercise of their procreative functions, but most of all, appropriate food obtained by the physical effort we term chase. All but the very last condition is supplied in a measure in well managed collections. The degenerating effect of the absence of chase must be admitted. An interesting and suggestive example of this was noted by Mr. Jones at the London Zoological Gardens. He observed the skull of a lion that had been in captivity thirteen years, in which the canine area of the face and the part of the skull acting as the insertion for the seizing and holding muscles had undergone atrophy while the chewing muscles with their bony bases had remained normal. Numerous examples of disease atrophy are on record and those of a physical nature must have counterparts in the realm of physiology. The size to which an animal will attain cannot be estimated by the examples seen in menageries. Judging by the accounts of collectors and hunters and upon the more reliable of the moving picture displays of wild animals in their native haunts, it would seem probable that under normal conditions of habitat the average size of wild beasts is considerably in excess of that in park specimens.

The effect of captivity may also be felt in the direction of reduced resistance to infectious diseases. Brooks, of the New York Park, expresses the view that captivity increases susceptibility to bacteria and causes parenchymatous degenerations. In the latter direction it is interesting to learn that Seligman of London claims to have seen sudden deaths in wading and struthious birds from myocardial disease, without valvular or other lesions, for which he holds the enervating effects of captivity responsible. It is well recognized that a species may be unusually susceptible to a disease that it has not encountered in its phylogenic development. Man illustrates this peculiarity very clearly. Europeans were found exceedingly susceptible to sleeping sickness when they went first to the part of Africa inhabited by the tsetse fly, and the American Indians died in hordes when they met the tubercle bacillus for the first time. Judging by the ravages of tuberculosis in captive monkeys a similar susceptibility probably explains the matter for there are no entirely satisfactory records of this disease among them in the wild state.

In so far as general susceptibility to infection is concerned, it may be in part due to one of the artificial conditions of captivity, that of inbreeding. This influence is undoubtedly very great, both by chance in families, and by intention on the part of dealers as well as the mating which occurs in menageries. However, it is not known how far inbreeding may go in the wild state so that one must be very careful about drawing conclusions in this particular. Several years ago, at the time we reported the neoplasms found at the Garden, discussion arose as to the effect of inbreeding, and thereafter some observations were made in this direction. With the exception of the hyperplasias of the thyroid, not certainly of neoplastic nature, in a much mixed-up family of wolves, we could find no evidence that inbreeding was responsible for tumors. Plimmer and Murray of London, seem to imply that some of their inbred animals are likely to have tumors; reference to this matter will be made later in this book. In so far as diseases of the organic systems are concerning those of the bones seem to be the only ones in which inbreeding is significant.

The individual resistance will be reduced of course by the unsanitary surroundings incident to trapping, shipping and storage, but this need not affect the figures or pathological tendencies of classes or orders.

The effect of captivity is felt in another way. A very large percentage of wild life perishes during the first weeks or months after its capture, and in gardens the heaviest mortality occurs among the recent arrivals. The London Garden figures that from thirty-three per cent. to fifty per cent. of their total mortality is in animals that have not been in the garden six months and that die because they are not yet accustomed to their new surroundings. It seems to us, both from an academic and a practical standpoint, that this is a long time and should afford ample opportunity for the garden to study the specimen and for the specimen to become acclimated. These early deaths are perhaps to be ascribed in large part to failure of acclimatization but many are doubtless the result of infection acquired in the wild, in transit while in the hold of vessels, at quarantine, or in trains, or at the establishments of dealers. We have seen a few deaths which have followed behavior that might be likened to homesickness. Perhaps the age at arrival has an influence upon the morbidity and mortality of wild animals, for it is easily conceivable that the young and the very old might adapt themselves to new surroundings with much less readiness than the sturdy middle-aged adult. The age of animals upon arrival is very rarely known, and can only be recorded as “young,” “fully developed,” and “old.” This will have an effect upon statistics and when possible is noted in the text, but this is not practicable to the extent we desire. The meaning of “young,” “adult,” and “old” is not the same throughout the animal orders nor even within orders.

Mitchell has attempted to gain concrete ideas of the expectancy of life among animals by analyzing the records of the London Gardens. This gentleman bases his figures upon known ages and the length of time in captivity, from a combination of which data the specific viability and the potential longevity may be estimated. Such results, he admits, can only be approximate and they show within classes and orders, a decided lack of uniformity. The terms “specific” and “potential” longevity, coined by Sir Ray Lankester, apply, for the first, to the average length of life as it is affected by external conditions and those incident to procreation, while, if an animal be under ideal conditions it will attain the potential longevity which is longer than the former. These considerations have a biological and economic importance, while a knowledge of the pathology shown by the various groups may help to explain these durations of life. Contrariwise figures of the expected longevity may assist us in evaluating youth and senility in the causes of death but can hardly affect the comparative nature of the lesion.

A résumé of Mitchell’s studies indicates that the higher apes have a potential longevity and a hardihood much less than man but still upwards of thirty years. As one investigates lower in monkeys, life periods become shorter, while in the next order, Lemures, the length of life rises. Carnivora have a reasonably good vitality, their potential periods varying from ten years in the foxes to thirty-three years in bears. Insect eating animals are short lived, three years being a maximum. The Bat family shows great variations, the greatest life being not over seventeen years. The Rodentia have long lives compared to their sizes—twenty years in porcupines, fifteen years in squirrels, thirteen in marmots, nine in agoutis and capybaras, and three in dormice (which is also about the maximum for the rat). Hyraces live four years on the average. Proboscidea, although reputed to live to great age, probably rarely live a half century and may be said to have an expectancy of twenty to thirty years. Perissodactyla (horses, tapirs and rhinoceroses) while they may live half a century, have an average life of between fifteen and thirty years. The closely related Artiodactyla fall into two groups, a first comprising antelopes, sheep, goats and deer which rarely exceed seventeen years, and a second consisting of cattle, camels and giraffes, which vary in expectancy from eighteen to thirty years. The smaller members of the Ungulata have in relation to size a relatively greater viability, the ruminants, however, having on the whole a low viability. Marsupials vary from a maximum of seven years in the opossum to eighteen in the wombats, but none of this group has a good viability. The Aves as a class or if compared according to dietary requirements, have longer potential ages and better viability than mammals. Passerine birds average twenty years and many live to sixty, while the Picariæ approach the former figure but do not have such good viability. Psittaci and Striges may live a half century but the resistance of the latter is much reduced by any unfavorable surroundings. The raptatory birds live fifty years, but their viability is variable. Herodiones have a maximum expectancy of thirty years and good resistance, while their relatives, Steganopodes, may live fifty years, and Odontoglossæ have a good viability, up to twenty years. Anserine birds may live to be fifty, and, unless conditions are quite unfavorable, have a good resistance. Columbæ may under good conditions live to be fifty. Gallinaceous birds may only be expected to survive twenty years, a figure also given for Fulicariæ. Alectorides may live up to fifty years. Limicolæ, though they do not thrive in captivity, may live thirty years. Impennes live poorly under artificial conditions, the greatest record being twelve years, a figure also holding for Crypturi. Struthiones, if the conditions be right, may live fifty years.

Because of the variable specific longevities, it is frequently difficult to decide when an animal is senile. Man is said to be as old as his arteries, and his span of life nowadays is in the neighborhood of half a century. Parrots exhibit lesions of the vascular system comparable to the arteriocapillary fibrosis of human beings, and their expected longevity is about the same or a little greater. From a study of our cases of this lesion in parrots it can be said to appear quite early in life and not to lead to organic disease as it is alleged to do in man. It is, however, interesting to note that in those animals which are supposed to have the longest specific lives—elephants, snakes, anserine and raptatory birds, parrots—there is relatively low mortality and fewer infectious diseases are encountered. The last part of this statement should be qualified by stating that anserine birds and parrots are quite susceptible to mycoses, in all probability from musty food, which raises their death rate, but as this is accidental and artificial, it can be excluded from consideration.

In a rough way there is a direct relationship between the size of an animal and its longevity, but this is not close enough to be a reliable guide; whales and elephants live a long time, but so do snakes and parrots. Within orders this relation of size and expected longevity is more easily seen but is not absolute. I cannot state, according to my present studies, that there is an unqualified relationship between the size and expected longevity of an animal and its pathological lesions.

The immediate surroundings and the management of captive animals have a very direct and important bearing upon the mortality and perhaps upon the incidence of morbid processes but probably not upon the character of the latter. A full knowledge on the part of the personnel of a zoological society concerning the habits and habitat of every animal in their keeping is essential, to which must be added a group of interested keepers. In engaging the last, it should not be forgotten that certain men have “a way” with animals and that others cannot manage themselves.

The enormous literature at the disposal of the naturalists permits executive officers to formulate a plan of housing and feeding with fair accuracy for each kind of animal, but of course it is rarely possible to obtain in sufficient quantity the natural food (e.g., ants for anteaters). In so far as food is concerned it seems that with a few exceptions like the one just mentioned, the substitutions made at the zoological gardens are nearly satisfactory. The elements in which the captive diet is poor are the inorganic salts and vitamins since Dr. Corson-White, some of whose work is included in a later chapter, has shown that for those animals which our statistics indicate as most prone to have rickets and osteomalacia, the available phosphorus and calcium are low, and one vitamin was also below the desired quantity. In this regard, however, I am not at all convinced that diet alone will suffice to explain these degenerative osseous diseases; I shall take this up more fully later. Careful inspection of all food should be made and cleanliness (sifting of cereals, protection of meat from flies, etc.), is indispensable. The mortality among our carnivora has materially decreased since the horse meat after butchering was placed in covered galvanized iron pans. There are many problems of feeding, too numerous to be covered in a survey of this sort, which must be solved, and it is a credit to superintendents that this they have studied carefully.

There are two problems in the management of animals upon which much difference of opinion exists, namely the heating of houses and the material of which cages are made. It seems to be the practice in many gardens to keep animals very warm. Dr. Chalmers Mitchell states unqualifiedly that adult animals do not have to be kept warm, and that even an equable temperature is not demanded, variations in temperature having a distinctly stimulating effect. However he maintains that they should be kept dry and must be supplied with a shelter. This is in accord with the experience at the Philadelphia Garden, since for many years we have allowed access to the open air all winter to every animal that could stand it. A large group of macaques has now lived entirely in an open “band stand” cage for nine years with a lower mortality than in the rest of the monkey collection, which is permitted to go indoors some of the time. Occasionally one in poor health is frozen to death, and healthy ones may lose fingers, toes, or a part of the tail, but the general condition is so much improved that they present an attractive exhibit to visitors. Unless a storm be of great severity, wild animals are usually indifferent to it although they may seek their shelter. Snow apparently is no source of fear to them, and many enjoy playing in it. The general principles of the enclosure should be proper lighting, free access of air, dryness and shelter in time of storm, the last so arranged that the sleeping place is well protected. Appropriate arrangements should be made for nocturnal animals, regardless of their visibility to visitors, if their preservation is of importance.

The hygiene of communicable disease has influenced everyone to use concrete and metal for cages. These substances are without doubt most simply kept clean, but they are heat-conducting and remain cold or damp longer than wood or the ground. It may be claimed that the latter two cannot be disinfected so well, but this need not militate against their use. Wood can be disinfected by sunlight or by mechanical cleaning plus disinfectants, by a blast lamp and by paint. The ground will disinfect itself if allowed to lie fallow for a time, or it may be turned over after sprinkling with lime. It is fair to note that the New York Zoological Garden reduced their mortality, especially from verminous pneumonia, by changing some deer herds to concrete paved enclosures; if that were the only change made the result would be very significant, but it should not be forgotten that another clean ground range might have served as well to a herd from which the infected ones had died. My own observations with guinea-pigs, rabbits, mice and dogs lead me to believe that they thrive and breed better on wooden floors than on metal or stone.

I have tried to work out figures to show that more animals die when housed in enclosures of stone and metal than when upon the earth or on wood, but the attempt has been unsuccessful chiefly because of the presence of epidemics and parasites, principally among the birds. The attempt was further embarrassed because some members of an order are housed on both floorings. However, there was no great advantage for the metal and concrete floors even after the epidemic had been discounted. This Garden does not have a great number of pneumonias, a disease said to be favored by dampness and cold, but those that occur are chiefly among the small mammals, on wooden floors and in the large bird house in cages of concrete and metal. However, the construction of both these houses permits the visitors to approach very close to the cage, a factor that doubtless explains the disproportionate incidence of inflammation of the lungs. In so far as outdoor fowl and ungulate ranges are concerned, they should be changed frequently under the best conditions since occasionally one will find groups doing badly until moved. Moreover the ground becomes contaminated with parasites such as esophagostomum and heterakis, infestation with which while not very serious in itself, may lead to fatal infection with bacteria.

The effect of animal parasites upon the morbidity and mortality of wild beasts and birds in captivity is by no means clear, and Doctor Weidman and I are inclined to be sceptical, with certain reservations of course, of their great importance in the death rate. Doctor Weidman has kindly agreed to contribute a chapter upon the general distribution of protozoal and metazoal parasites with a summary of their probable pathogenic importance.

The groups known to have a decided pathological power might be divided into the toxic, the tumor formers and the mechanically obstructive; certain parasites have properties placing them in two of these classes. The first group comprises the hemosporidia and hemogregarines, the uncinaria and some of the cestodes, forms which produce hemolysis and hemorrhages with varying grades of anemia. The importance of this group is shown chiefly among the Aves, in which high grades of anemia are occasionally met from malarial infections, but cats and dogs or even herbivores also frequently suffer from hookworm. The tumor-producers are chiefly echinococcus worms, the cysts of which may grow large enough to occupy nearly the entire abdomen. A certain grade of anemia and general ill health accompany this hydatid disease, partly the result of a toxin and partly by damage to important viscera. Those parasites which obstruct mechanically do so by their own bulk or by an accompanying inflammation, incited by them as foreign bodies or by bacteria which have gained entrance at the irritated point. This is exemplified by the enormous collection of nematodes sometimes found in reptiles (a pailful was removed from a python) and by the tightly coiled or tangled thread and tape worms frequently found in birds. The effect of swelling by the mucous membrane under the influence of worms is illustrated by the infestation of the proventricle in parrots. Here spiroptera penetrate into and under the glandular layer which swells and pours out mucus, the total mass of nematodes, mucus and tissue obstructing the passage.

Very many animals show parasitic infestation at postmortem, but the percentage in which they can be said to be principal causes of death is quite small, while that in which they play a rôle as activator of the terminal condition is also small but indeterminate. The latter group comprise, together with the anemias mentioned above, certain forms of pneumonia, of hepatic and vascular lesions. Inflammations of the lungs from ascaris and paragonimus are fairly well known; fortunately we have been troubled less with this than have most gardens, possibly because we do not have such large herds of herbivora susceptible to it. Hepatic diseases from flukes, from coccidia and from amœbæ we have always with us in small numbers, but they are unimportant excepting enterohepatitis, a condition which appears in nearly all orders. This last disease, be it purely amœbic as in dysentery of man and monkeys, or like blackhead of turkeys and chickens or in the forms of quail disease, arrests the attention at once and evokes a desire to explain the association of large intestines and liver. Parasitic vascular lesions are relatively unimportant.

Taking parasitic infestations by and large, there are close similarities throughout the entire animal kingdom, and the effects produced by a given genus will be repeated almost exactly in several others. The pathological pictures of anemia, of hepatic degeneration, of cystic degeneration, of colonic ulceration or of fibroses are similar in different hosts, only slight variations in the type of inflammation being noted, for instance in reptiles and birds as against the mammals. We have made rather close observations upon the effect of parasites in the production of neoplasms, incited by Fibiger’s discovery of nematodes in the rat’s stomach cancer, but, with the possible exception of a papillomatous growth in the stomach of opossums from the action (?) of physaloptera, we have been unable to establish such an etiological relationship. A decision of the importance of parasites in any given case is not without its difficulty, and we are inclined to reserve judgment pending further analysis unless the effect of the invaders is unequivocal. Leiper does not seem to credit animal parasites with a great effect on the mortality after a specimen has been in the collection six months since all the intestinal varieties he studied came from animals dying in that period. On the other hand the forms which invaded the internal organs and tissues were, in his series, from specimens resident several years in the garden. He seems to think the conditions of life at the garden favor the expulsion of intestinal worms. To what extent some intestinal worms may be commensal remains as uncertain as the value of certain bacteria in the gut tract. In man considerable importance has been ascribed to certain fermentative and putrefactive germs in the maintenance of a reaction unfavorable to strict pathogens and some observers have looked at them as possessing a digestive power. In the digestive tract of the animals eating large quantities of carbohydrate as cellulose, nature provides for its use by rumination and by supplying a large hind-gut, by which means secondary mastication and bacterial decomposition of the cellulose capsule insures its full use. Possibly a similar usefulness may be finally ascribed to some animal microbes or even larger metozoa.

The rôle of vegetable parasites in the causation of disease among wild animals seems as undoubted as it is in the human being and the pathologic results are usually as clear, at least for the entities of which we have exact data, based upon comparisons with man and domestic animals.

There seems to be no essential difference among mammals between the pathological pictures of infectious septicemias, the mucous and serous membrane inflammations and tuberculosis for example. They are characterized by fibrinous, purulent or infiltrative inflammations which may go on to necrosis or repair, by fever, by leucocytosis and by evidences of resistance—all of these things occurring in a similar way throughout the class. Of course not all animals are receptive to all infections since specific racial and generic immunities exist, but the basic response in terms of pathology is similar. There are no normal means of judging the susceptibility of wild animals on their native heath to the important pathogens of civilization, pneumococci, streptococci, staphylococci, cholera bacilli, the typhocolon group, the Friedlander group and others, but it is interesting to note that in captive conditions they evince some receptivity to these germs or their congeners. The pneumococcus takes a fairly heavy toll in zoological collections every year and the Friedlander bacillus, not a very common cause of human pneumonitis, has been seen here and at London.

Among the birds, however, quite distinct differences in some pathological processes occur, not only from the mammals but also within the class. As a whole birds do not produce pus as we know it in man, probably because of the absence from their leucocytes of a protein- splitting ferment; their leucocyte-producing organs do not seem to respond as readily to a virus, the place of purulent exudate being taken by a coagulum or necrosis. The former varies from a clear gelatin-like material seen upon serous surfaces to a thick mat or mass of coarse but short fibrinous strands. Necrosis may succeed upon the latter or occur so promptly as to appear like the original form of degeneration. It is usually rapid, accompanied by a circumferential congestion but not associated with active phagocytosis. Giant cell production is variable, but when developed the appearance is like that of large syncytia. Hemolysis is not marked in the simple infections but a hyperplasia of the mononuclear nodes of the liver is the rule. The function of this nodal increase is not quite clear. It has been always thought that the scanty bone marrow would supply the necessary erythrocytes, but we have seen these mononuclear areas full of pale red cells fitted with round nuclei and without pigment. The fibrin mentioned above does not have the delicate interweaving that we know in a fibrinous exudate in man. This is interesting when we consider the composition of the blood and its coagulation in the Aves. The cell upon which human coagulation seems to depend, the platelet, is represented in birds by the thrombocyte, which appears only up to about 50,000 per cubic millimetre. Coagulation time is relatively short and the resulting clot is firm and irregular. Perhaps this may have something to do with the nature of an inflammatory exudate.

The response to infection on the part of birds may to some extent depend upon differences in anatomy, which are quite distinct, not only from the mammals within which class the anatomy is more uniform, but also from one avian order to another. These differences among the birds may be exemplified by the large foramina between lungs and air sacs in the water birds, a passage which permits infection, notably mycosis, to spread from the first to the second. Again the close apposition of the pancreas to the duodenum over a long stretch permits easy infection of the former from the latter. Still again the large renal-portal vein in the gallinaceous birds explains some of the infections of the liver secondary to intestinal disease. The position of the lungs, deep in the thorax and fitted into recesses made by the sharp anterior border of the ribs and overlaid anteriorly by a rather firm air sac wall, makes it difficult for these organs to expand and therefore renders even a simple congestion a dangerous thing. The position of the ovary subjects the shell-less egg to much danger from the intestinal area.

These and many other peculiarities of anatomy affect the pathological picture in birds. To be sure there are also noteworthy differences among the Mammalia, notably in the intestinal and genital tracts, but the pathologic response is not so varied as in the birds. When due allowance is made for the kind of stomach and absorptive area, apparent differences can be reconciled. For example, there is little confusion experienced in comparing acute erosive gastritis or the follicular enteritis of an omnivorous intestinal tract (man or pig), of a sacculated stomach and absorptive tract (the marsupial), of a carnivorous gut (cat) or a herbivorous compound stomach with its long digestive and water-absorbing surface (cow or camel) and an expansive muscular organ with a very extensive digestive area (seal). The type of lesion seems the same, in that inflammation, pus, necrosis, granulation tissue and cicatrices are comparable throughout the series. The size of the hind-gut has been taken by Metchnikoff as an indicator of the possibility of intoxication by degradation products of digestion. He believes that the capacious colon of herbivora and the short small one in carnivora explain the relatively greater life in the latter, because here less stagnation and absorption can take place. A reference to the expected lengths of life given before hardly substantiates this, and in our later chapters there will be found no strong indication that animals with large colons suffer with degenerative visceral changes more than those with small ones; nay even the reverse may be found true.

In regard to epizoötics the behavior of man and lower animals is similar except perhaps that during an outbreak a smaller percentage of the latter give evidence of individual immunity and whole groups are apt to be carried off. Occasionally hygienic measures stay the ravages, at other times nothing seems to avail. Fortunately it is sometimes possible to sacrifice infective specimens and remove contagion. We have had few serious outbreaks, unless one might call our former heavy infection with tuberculosis in monkeys an epizoötic. The principal ones were an unexplained water fowl disease which carried off one hundred and forty- six birds, an imported epizoötic of quail disease which killed about the same number, a few cases of blackhead among wild turkeys, and a small group of cases of amœbic dysentery in monkeys and of thrush in passerine birds, and a small number of tuberculous pneumonias in snakes.

Pathology may be difficult upon an anatomical basis, but when we engage to explain functional physiological defects we are surely embarked, with a poor compass and weak rudder, upon an uncharted sea. One knows, of course, that all animals require the same amount of food elements per kilo of body weight, that man eliminates his nitrogen as urea and uric acid, that monkeys do the same, that most other mammals destroy uric acid and excrete allantoin, that birds and reptiles form uric acid but chiefly urates, that there is an adaptation of alimentary tract and diet, that herbivores have a high threshold for carbohydrates, that there is a variable quantity of enzyme present in different organs and in different animals, that vitamins, whatever they may be, are necessary for the growth of young animals, that hormones exist whereby correlations of parts are kept normal—but these things, rather than being learned thoroughly from animals, have merely been substantiated by comparisons with man. Constitutional diseases so-called, from which the necessity to investigate much of this physiology originated, are little known in the wild animal. Many cases of so-called gout have been encountered and we have seen an instance of diabetes in a fox, but more extensive experience is needed for definite practical comparisons. This applies to thyroid and pituitary disorders and to the vague conditions we have at times been obliged to call marasmus or inanition.

Some attention has been given to the study of diets for the wild specimens of our Garden, but no systematic observations have been made or records kept upon purely physiological subjects. Reference will be made at appropriate places to accepted comparative physiological facts, but our statistics permit additions to such knowledge only in a limited manner and in isolated instances. Doctor Corson-White has very ably summarized the diet, alimentary tract and physiology of the zoological groups with the pathology as found in our records.

A word might be added here as to the destruction of animals by injury from fighting and harassment by others in the cage. Fighting doubtless causes death, especially when males are together, but it is our experience that in cases of traumatic death search should always be made to see if the resistance of the dead animal had not been reduced by some disease. This is well illustrated in birds. Very frequently a specimen will come to autopsy with its head feathers plucked out, or with a billthrust in the wing or pelvic region. Such birds are not infrequently suffering from malaria, or heavy intestinal parasitism or from organic disease whereby the resistance and self-preservatory power has been decreased.

The foregoing survey of the approach to our subject reveals the multiplicity of factors which affect the study of comparative pathology. No one of them can be entirely omitted, no one is without some effect upon the origin and expression of disease, and no one is fully understood. Yet it is to be hoped that a study of our material, accumulated under routine conditions and uninfluenced by any experimental procedures, will demonstrate the natural response of various zoological groups to morbific agencies. Perhaps reactively some of the modifying conditions may thus be understood. It is also not unreasonable to expect that alterations observed as natural responses in a large number of specimens in nearly normal surroundings would serve as more reliable guides to investigative speculation than would changes in a few animals under artificial technical experimentation. We hope that the few facts we have been able to record may afford someone a basis for further biological studies. It is also to be hoped that something has been learned which in the end will afford an explanation of the diseases of man. Too great optimism in this direction should be guarded against because the human being is indeed an animal sui generis and, from the standpoint of normal conditions of nature, a wild animal.

The zoological classification found on pages 43–46 was compiled in 1903 by Dr. A. E. Brown on the basis of the British System. With a few exceptions the computations in the text are made on the basis of zoological orders since the number of specimens in families is often too small and the complications of so many different figures would be confusing. The tables will be found to correspond to the sequence of the classification. Dr. Corson-White has, however, used for her analysis the dietary groupings. A carnivore in her chapter implies strictly a meat- eater, in the rest of the book one of the zoological group Carnivora.

The Laboratory of Comparative Pathology at this Garden speaks for the earnest desire on the part of the Directors to use the material to its fullest extent, and I, acting for myself and my associates, wish to record our appreciation of the facilities offered to us for study, and for the broad-minded, scientific coöperation the Board has always displayed. The President, Charles B. Penrose, M.D., Ph.D., LL.D., was the active originator of the plan whereby this department was started, and he has given to it continuously the support of his rich experience. I wish to express for myself the deepest appreciation of his personal interest in my studies, and assistance which has been constructive and stimulating. Whether or not this present work prove useful to the extent that is hoped, the results from the Laboratory are such as to make the scientific world debtor to this gentleman.

It is a duty, and a pleasant one, to record, though unfortunately in memoriam, my association with Arthur Erwin Brown, A.M., Sc.D., Ph.D., C.M.L.Z.S., for many years the Secretary of the Society and Executive Officer of the Garden. Doctor Brown as teacher was ever ready to help in the broad subject of biology, and I am proud to recall that he guided me also as a friend.

The first director of the Laboratory was Courtland Y. White, A.M., M.D., who served from 1901 to 1906, retiring then to accept a position in the City Laboratory. The foundation of the recording system is still in use essentially unchanged from his plan, and is a credit to his foresight. Our clerk and technician, Miss Harriet M. Phelps, has served the Garden faithfully and well since 1906. The condition of the museum is very much due to her interest and watchfulness. Thanks and appreciation for her work are felt by every one, the author most of all. Dr. F. D. Weidman has been our first assistant since 1911, and his work on parasitology has been of the greatest value, practically and scientifically. It is to be hoped that we shall be able to retain him indefinitely. Dr. E. P. Corson-White has in recent years taken an assistant position with us, armed for the work with a thorough knowledge of applied organic chemistry and immunology, and has already obtained useful results.

ZOOLOGICAL CLASSIFICATION │

MAMMALIA

PLACENTALIA

PRIMATES

Simiadæ Anthropoid apes

Cercopithecidæ Old World monkeys (macaques, baboons).

Cebidæ New World monkeys (capuchins, howlers, spiders).

Hapalidæ New World monkeys (marmosets).

LEMURES

Lemuridæ Lemurs, Loris, Galagos.

CARNIVORA

Felidæ Cats

Viverridæ Civets, Genets, Paradoxures, Ichneumons.

Hyænidæ Hyena.

Canidæ Dogs, Wolves, Foxes, Jackalls, Etc.

Mustelidæ Marten, Skunk, Weasel, Otter, Badger, Etc.

Procyonidæ Raccoon, Bassaris, Coati, Kinkajou.

Ursidæ Bear.

Otariidæ Eared Seal, Sea Lion.│These are grouped │separately as suborder, │PINNIPEDIA, illustrating │water carnivores.

Phocidæ Common Seal, Walrus. │ „

INSECTIVORA

Tenrecidæ Tenrec.

Solenodontidæ Solenodon.

Talpidæ Moles, Shrews.

Erinaceidæ Hedgehog.

CHIROPTERA

Pteropodidæ Fruit Bats, “flying foxes.”

Vespertilionidæ Common bats.

Emballonuridæ Snouty Bats, Free-tailed Bats.

RODENTIA

Sciuridæ Squirrels, Spermophiles, Marmots.

Castoridæ Beaver.

Muridæ Rats, Mice.

Geomyidæ Pouched Rats, “Gophers.”

Dipodidæ Jumping Mice, Jerboas.

Heteromyidæ Kangaroo Rats.

Octodontidæ Capromys, Coypu.

Hystricidæ Porcupines.

Chinchillidæ Viscacha, Chinchilla.

Dasyproctidæ Agouti, Spotted Cavy.

Caviidæ Guinea-pig, Capybara.

Leporidæ Rabbits, Hare.

PROBOSCIDEA Elephant.

HYDRACOIDEA Cape Hyrax.

UNGULATA

PERISSODACTYLA (odd toed)

Rhinocerotidæ Rhinoceros.

Tapiridæ Tapir.

Equidæ Horse, Ass.

ARTIODACTYLA (even toed)

Bovidæ Oxen, Antelopes, Sheep, Goats.

Cervidæ Deer, Moose, Elk.

Antilocapridæ Prong-horned Antelope.

Giraffidæ Giraffe.

Tragulidæ Chevrotains, Muis Deer.

Camelidæ Camels, Llama.

Hippopotamidæ Hippopotamus.

Suidæ Swine, Warthogs.

Tayassuidæ Peccaries.

SIRENIA Sea-cow, Manatee, Durong.

CETACEA Whales, Porpoises.

EDENTATA

Bradypodidæ Sloths.

Dasypodidæ Armadillo.

Myrmecophagidæ Anteaters.

MARSUPIALIA

MARSUPIALIA

Didelphyidæ Opossums.

Dasyuridæ Dasyures, Tasmanian “Devils.”

Peramelidæ Bandicoots.

Phascolomyidæ Wombat.

Phalangeridæ Phalangers.

Macropodidæ Kangaroo, Wallabies.

MONOTREMATA

MONOTREMATA

Echidnidæ Echidna, Ornithorhynchus.

AVES

PASSERES

Turdidæ Thrushes, Robins, Etc.

Sylviidæ Warblers, Kinglets.

Paridæ Titmouse.

Troglodytidæ Wrens, Mockingbirds, Catbird, Etc.

Pycnonotidæ Bulbul.

Crateropodidæ Babblers, Jay-thrushes.

Oriolidæ Oriole.

Motacillidæ Wagtails.

Dicruridæ Drongos.

Mniotiltidæ Chats, Warblers, “Woodwarblers,” Etc.

Cœrebidæ Sugarbirds.

Vireonidæ Vireos.

Laniidæ Shrikes.

Ampelidæ Waxwing.

Hirundinidæ Martins, Swallows.

Meliphagidæ Honeyeaters.

Tanagridæ Tanagers.

Ploceidæ Weavers, Whydah birds, Waxbills, Finches, Etc.

Fringillidæ Finches, Sparrows, Buntings, Grosbeaks, Etc.

Icteridæ Hangnests, Troupials, Grackles, “Blackbird,” Etc.

Sturnidæ Starlings, Mynahs.

Corvidæ Crows, Jays, Magpies, Jackdaws.

Alaudidæ Larks.

Tyrannidæ Tyrans.

Cotingidæ Bellbird, Cock-of-the-rock, Etc.

PICARIÆ

Upupæ Hoopæ.

Trochilidæ Hummingbirds.

Cypselidæ Swifts, “Chimney Swallow.”

Caprimulgidæ Night hawk, Whip-poor-will.

Coraciidæ Roller.

HALCYONES

Alcedinidæ Kingfisher.

Momotidæ Motmots.

BUCEROTES

Bucerotidæ Hornbill.

TROGONES

Trogonidæ Trogons.

SCANSORES

Picidæ Woodpeckers.

Rhamphastidæ Toucans.

Capitonidæ Barbets.

COCCYGES

Cuculidæ Cuckoos.

Musophagidæ Touracous.

PSITTACI

Loriidæ Lories, Lorikeets.

Cacatuidæ Cockatoos.

Psittacidæ Macaws, Conures, Amazons, Parrots, Parrakeets.

STRIGES

Strigidæ Barn owl.

Bubonidæ All other owls.

ACCIPITRES

Falconidæ Buzzards, Hawks, Falcons, Eagles, Etc.

Serpentaridæ Secretary Vulture.

Catharidæ Vultures.

COLUMBÆ

Treronidæ Fruit pigeons.

Columbidæ All other pigeons and doves.

PTEROCLETES

Pteroclidæ Sand grouse.

GALLI

Tetraonidæ Grouse, Ptarmigans.

Phasianidæ Pheasants, Fowls, Turkeys, Quail, Etc.

Cracidæ Curassows, Guans, Etc.

Megapodidæ Brush turkey.

HEMIPODII

Turnicidæ Hemipodes.

FULICARIÆ

Rallidæ Rails, Porphyrios, Gallinules, Coots, Etc.

ALECTORIDES

Aramidæ Courlan.

Eurypygidæ Sun bittern.

Gruidæ Cranes.

Cariamidæ Cariama “Crane.”

Psophiidæ Trumpeters.

LIMICOLÆ

œdicnomidæ Thicknees.

Charadriidæ Plovers, Sandpipers, Curlews, Woodcocks, Etc.

Chionidæ Sheathbills.

GAVIÆ

Lariidæ Gulls, Terns.

Stercorariidæ Jaeger Gull.

PYGOPODES

Colymbidæ Loons, Grebs.

Alcidæ Auks, Murrs, Puffins.

IMPENNES

Spheniscidæ Penguins.

STEGANOPODES

Sulidæ Gannets.

Pelicanidæ Pelicans.

Phalacrocoracidæ Cormorants.

Anhingidæ Darter “Water turkeys.”

TUBINARES

Procellariidæ Petrels, Fulmars.

HERODIONES

Ardeidæ Herons, Bitterns, Egrets.

Ciconiidæ Storks, Ibises.

Plataleiidæ Spoonbills.

ODONTOGLOSSÆ

Phœnicopteridæ Flamingoes.

PALAMEDEÆ

Palamedeidæ Screamers.

ANSERES

Anatidæ Swans, Geese, Ducks.

STRUTHIONES

Apterygidæ Kiwis, Apteryx.

Casuariidæ Cassowaries.

Struthionidæ Ostriches.

Rheidæ Rheas.

CRYPTURI

Tinamidæ Tinamous.

List of Animals subjected to Autopsy giving the number of each. These Figures are used to obtain the percentages quoted in the Tables and Text.

MAMMALIA Primates 498 Lemures 86 Carnivora 481 Pinnipedia 20 Insectivora 6 Chiroptera 5 Rodentia 198 Ungulata 365 Proboscidea 3 Hyracoidea 7 Edentata 16 Marsupialia 175 Monotremata 0 1860 ————

AVES Passeres 1355 Picariæ 87 Striges 133 Psittaci 689 Accipitres 196 Columbæ 157 Pterocletes 0 Galli 299 Hemipodii 2 Fulicariæ 35 Alectorides 37 Limicolæ 6 Gaviæ 20 Pygopodes 0 Impennes 5 Steganopodes 21 Tubinares 0 Herodiones 98 Odontoglossæ 6 Palamedes 5 Anseres 317 Struthiones 32 Crypturi 5 3505 ———— ———— 5365