Part 13

But, although the typhoid bacillus appears to submit and meekly succumb to this plan of campaign, yet the conclusion must not be rashly drawn that all descriptions of bacteria will be equally feeble and helpless in these circumstances.

Doctors Percy Frankland and Templeman have shown that the spore form of the anthrax bacillus is able to successfully challenge all such attempts upon its vitality. Thus when put into water and frozen at a temperature of -20° C., the process being extended over a period of three months and interrupted no fewer than twenty-nine times by thawings, when examined even after this severe series of shocks, it showed no signs of submission and clung to life as tenaciously as ever.

The more sensitive form of anthrax, however, the bacillus, was readily destroyed; for after one freezing its numbers were already so much reduced that it was only with difficulty that even one or two could be found, and after the second freezing every one out of the large number originally present had died.

Renewed interest has been of late revived in the question of the behaviour of bacteria at low temperatures, in consequence of the possibility of obtaining, by means of liquid air and liquid hydrogen, degrees of cold which were undreamt of by the scientific philosophers of fifty years ago. Public interest has also been quickened in such inquiries on account of the important part which low temperatures play in many great commercial developments, their application rendering possible the transport from and to all parts of the world of valuable but perishable foodstuffs, thus encouraging local industries by opening up markets, and bringing prosperity to countries and communities which before were seeking in vain an outlet for their surplus produce.

The application of cold storage for preservation purposes is, however, no novelty; for nature ages ago set us the example, and of this we have been lately reminded afresh by the discovery announced by Dr. Herz of a mammoth in Siberia, which, despite the thousands of years which have elapsed since it was originally overwhelmed and frozen, is described as being in a marvellous state of preservation.

Thus we are told that "most of the hair on the body had been scraped away by ice, but its mane and near foreleg were in perfect preservation and covered with long hair. The hair of the mane was from four to five inches long, and of a yellowish brown colour, while its left leg was covered with black hair. In its stomach was found a quantity of undigested food, and on its tongue was the herbage which it had been eating when it died. This was quite green."

Considering that certainly more than eight thousand years had elapsed since this creature was peacefully consuming what proved to be its last meal, nature's method of cold storage must indeed be regarded as unsurpassable in the excellence of its results.

I believe it was in the year 1884 that the first attempts were made to follow more closely and in greater detail the precise effect upon different bacteria of submitting them to temperatures of such a low degree as -130° C., obtained by means of solid carbonic acid. These experiments were carried out by Pictet and Young, and are recorded in the Comptes Rendus of the Paris Academy of Sciences.

They differ from those which we have so far been considering, inasmuch as the bacteria were not frozen in water, but in culture-material, or, in other words, like the mammoth, whilst enjoying a midday meal!

One of the micro-organisms experimented with was a bacillus known at that time as the rinderpest bacillus, capable of producing disease in animals when inoculated into them and existing both in the spore and bacillar form. Pictet and Young specially state that the spore form was present in the specimens employed by them, and hence the fact that this micro-organism was alive after being frozen and exposed to this low temperature of -130° C. for the space of twenty hours is not, perhaps, so surprising when we bear in mind the remarkable feats of endurance exhibited by spores which have with justification obtained for them a prominent place amongst the so-called curiosities of bacteriology. But of more interest than their mere survival in these circumstances is the fact that, on being restored to animation--or, in other words, released from their ice-prison--these bacteria were discovered to have retained all their pathogenic properties, this period of enforced rigidity having in no way affected their disease-producing powers.

Such results naturally only served to whet the scientific appetite for more, and the liquefaction of air and of hydrogen placing much lower temperatures at the disposal of investigators, those bacteriologists who were fortunate enough to command a supply were not long in availing themselves of the opportunity thus given them of further testing the vitality of micro-organisms.

Botanists had already shown that exposure to liquid air, which means a temperature of about -190° C., and to liquid hydrogen, which means a temperature of about -250° C., did not impair the germination powers of various descriptions of seeds, such as those of musk, wheat, barley, peas, vegetable marrow, and mustard, and that their actual immersion in liquid hydrogen for the space of six hours did not prevent them coming up when sown just as well as ordinary seeds which had not undergone this unique experience; hence the opportunity of submitting other members of the vegetable kingdom to these low temperatures was eagerly sought for by bacteriologists. Dr. Macfadyen found this opportunity in the laboratories of the Royal Institution, and, Professor Dewar having placed a generous supply of liquid air and liquid hydrogen at his disposal, he submitted specimens growing in various culture-materials, such as gelatin, broth, potatoes, etc., of typhoid, diphtheria, cholera, anthrax with spores, and other bacteria, for twenty hours and seven days respectively, to a temperature of about -190° C. In no instance, however, whether exposed when growing in fluid or solid media, could any impairment of their vitality or the slightest alteration in their structure be observed. Similar results were obtained when liquid hydrogen, or a temperature of about -250° C., was applied. The question of the retention or otherwise of the disease-producing powers of these bacteria was not investigated, and in this connection much interest attaches to Mr. Swithinbank's investigations on the vitality and virulent properties of that notorious malefactor amongst micro-organisms, the bacillus tuberculosis, when exposed to the temperature of liquid air. The specimens of the consumption bacillus employed were originally obtained from the human subject, and they were exposed for periods varying from six hours to six weeks to -190° C. In each case the malignant properties of the tubercle bacillus after exposure were tested by their direct inoculation into animals, and the results compared with those which followed similar inoculations made with bacilli which had not been frozen in this manner, but had been grown in ordinary circumstances. In no single case, Mr. Swithinbank tells us, were these frozen tubercle bacilli deprived of their virulence, and the length of exposure, at any rate as far as could be judged after six weeks, appeared to make no difference in this respect. It is true that the pathogenic action of the frozen bacilli appeared to be somewhat retarded--that is, they took rather longer to kill animals than the ordinary unfrozen bacilli--but in every case their inoculation produced the typical tuberculous lesions associated with them.

Of particular interest, however, in view of what has been already discovered about the lethal effect upon bacteria of violent alternations of temperature, are Mr. Swithinbank's observations on the vitality of the tubercle bacillus when exposed to such extreme variations of temperature as are represented by a passage from -190° C. to that of 15° C.

The bacillus tuberculosis is admittedly a tough antagonist to deal with, and enjoys an unenviable notoriety for its robust constitution amongst the pathogenic members of the microbial world; hence a knowledge of its behaviour in these trying circumstances, as we now know them to be to bacterial life, becomes of special interest. Great must have been the investigator's satisfaction, then, when he discovered that the vitality of the consumption bacillus had been so seriously impaired by this treatment that its pathogenic properties collapsed, and the animals which were inoculated with these specimens, instead of with the continuously frozen bacilli, suffered no inconvenience, and remained in good health.

But although no appreciable change either in the structure, vitality, or malignant properties of the particular bacteria investigated have been noted as resulting from their exposure to extremely low temperatures, yet there is no doubt that a certain proportion of the individual micro-organisms present--those probably whose constitution is less robust than their more fortunate associates--do succumb under these trying conditions.

This fact has been well brought out by Dr. Belli, of the University of Padua, in the experiments which he made with the fowl-cholera bacillus and the anthrax bacillus in the presence of very low temperatures. Thus he exposed a large number of fowl-cholera bacilli in broth to the temperature of liquid air, as many as 396,000 bacilli being present in every twenty drops of the liquid. After exposing them continuously for nine hours to -190° C., he had the curiosity, after thawing them, to count how many were left alive, and he found that an enormous mortality had taken place amongst them; for, instead of nearly 400,000 bacilli being present in one cubic centimetre, there were only about 9,000. On the other hand, in the broth tubes kept during that time in ordinary surroundings, the bacilli had flourished remarkably, and had greatly increased in numbers. Thus not only had no multiplication amongst these bacilli taken place, which circumstance is always regarded as indicative of their vital condition--not only, then, had their vitality been arrested--but a very large number of them had been actually destroyed in consequence of this severe treatment; but that the residue were not only alive, but unimpaired in their energies on being restored to animation, was proved by their being able to destroy animals, not having parted with any of their malicious propensities. Dr. Belli carried out similar experiments with the bacilli of anthrax and obtained very similar results. With regard to both these varieties of pathogenic bacteria, he mentions that their action upon animals was not quite so rapid as is characteristic of normal specimens of these micro-organisms, thus confirming the experiments in this direction made with frozen tubercle bacilli.

Not content with the exhibition of their powers of endurance, Dr. Belli determined to make yet another demand upon the vitality of these bacilli. For this purpose he immersed them in the liquid air itself, thus bringing them into direct contact with it, effecting this by lowering into the liquid strips of filter-paper soaked in broth containing these bacilli. But, in spite of remaining for the space of eight hours in these surroundings, they emerged triumphant, exhibiting no modification whatever either in their structure or pathogenic properties.

There are doubtless many other trials yet awaiting bacteria, to which they will most certainly be submitted before the limits of their powers of endurance have been adequately tested, but it is difficult to conceive of a severer strain upon their vital resources than the imposition of the conditions of which the above is but a brief sketch.

The triumphs achieved in this direction by micro-organisms are, however, closely approximated by the remarkable record established, according to the recent researches of Dr. Krause, by typhoid, anthrax, tubercle, and some other bacteria of preserving unimpaired not only their vitality but their virulence after having undergone for a period of twenty hours a pressure of no less than that of 500 atmospheres. When we reflect that a pressure of 500 atmospheres is equal to a pressure of about 7,500 pounds to the square inch, and that the normal pressure under which life is maintained upon this planet is approximately that of fifteen pounds to the square inch, this bacterial victory over physical conditions will be more readily appreciated.

The more intimate becomes our knowledge of bacteria, the more must we marvel at the equipment with which they have been provided for enabling them to maintain themselves in the struggle for existence--a struggle which is as severe and as remorseless in this lowly region as it is in those domains the inhabitants of which have risen to far loftier heights on the great ladder of life.

SOME POISONS AND THEIR PREVENTION

Little did the learned Dutchman Leeuwenhoek dream when, more than two hundred years ago, he recorded, in his Arcana Naturæ, that he had found "viva animalcula" in his saliva, that this, the first beginning of bacteriology, would lead, a couple of centuries later, to the inauguration of a new era in the treatment of disease, in which these so-called animalcula, from being considered as curiosities, would come to be regarded as powers for good and evil of the first importance. Protective inoculation or serum therapy, of which the public have lately heard so much in connection with diphtheria, is the direct outcome of bacterial investigations which during the last two decades have been pursued with such zeal in every part of the globe.

The vast domain of immunity, which until recently was an undiscovered country, is now being bit by bit annexed, and in all directions workers are engaged upon opening up new tracts, in overcoming difficulties, in changing chaos into order.

The problems which surround immunity are of so complex and subtle a character that their mastery is by no means either easy or rapid, and many recondite researches appear at frequent intervals on this subject in foreign and other scientific journals, rendering it a difficult matter to keep pace with the new discoveries and the latest theories.

The interest in this country in toxins and anti-toxins not unnaturally centres round that branch of the subject which deals with diphtheria, this disease having of late years figured so prominently in our mortality tables, whilst the production of diphtheria and other anti-toxic serums has been so finely elaborated abroad that it already constitutes an article of commerce, and doubtless helps to swell the exports of our great continental commercial rival.

In this connection the following statistics, published by Dr. Jalzer, of the Mülhaus Hospital, are of interest regarding the mortality from diphtheria before and after the introduction and application of diphtheria anti-toxin. The death-rate from this disease, writes Dr. Jalzer, which in 1892 and 1893 was fully 50 per cent., fell in 1895 to 38·5 per cent., in 1896 to 28·8 per cent., in 1897 to 16 per cent., to 20 per cent. in 1898, 15·15 per cent. in 1899, and 18·75 per cent. in 1900.

So far the efforts which have been made to mitigate human suffering have attracted most attention; but it will be remembered that Pasteur, before he commenced the study of hydrophobia, had already won his laurels in combating disease in the victory he gained over anthrax, the ravages of which so frequently decimated the herds of the French farmer and robbed him of his well-earned return on his capital and labour.

In summoning the brilliant Director of the German Imperial Board of Health to South Africa to investigate the nature of rinderpest, and, if possible, discover a means of protecting cattle from its onslaught, the Cape Government afforded another opportunity for the scientific study of a disease associated with animals, upon the successful mastery and limitation of which the agricultural prosperity of South Africa is so largely dependent, being as it is one of the most fatal and contagious maladies to which cattle are subject. Apart from the great commercial importance attending Dr. Koch's discovery of a device whereby cattle can be immunised or protected from contracting rinderpest when exposed to its contagion, this discovery is of great scientific interest, inasmuch as it has inaugurated a new departure in methods of immunisation.