Bacteria in Daily Life

The classical investigations of Pasteur on the attenuation of bacterial viruses such as those of chicken-cholera and anthrax, and his elaboration of a method of vaccination with these weakened viruses whereby the power of the disease over its victim is removed or modified, are too well known to require repetition here. The success which followed Pasteur's researches in this direction led him to undertake that great and difficult task, the prevention of rabies in the human subject – a task well-nigh superhuman in its demands, and one which only he could accomplish in whose life the pregnant words of a modern writer found expression – "il ne suffit pas de posséder une vérité, il faut que la vérité nous possède." The victory over this disease, which crowned a long life replete with brilliant achievements, has been universally recognised, and numerous institutes have arisen in all quarters of the globe for extending the benefits of this discovery for the relief of suffering humanity. These Pasteur or bacteriological institutes also furnish highly important centres where original research work of various kinds is carried on, and the stimulus which has thus been given to experimental science in the remotest parts of the world cannot be overestimated.

Methods for the prevention of disease have, however, not been confined to the elaboration and employment of modified or weakened bacterial viruses; the subject has been still more recently approached from another and quite different side. This new departure we also originally owe to France, although its practical development has been worked out in Germany.

It was in 1888 that two Frenchmen, Richet and Héricourt, communicated a memoir to the Comptes rendus of the Academy of Sciences, describing the curious results they had obtained with rabbits purposely infected with a disease microbe, the Staphylococcus pyosepticus. Some of the rabbits died after being inoculated with this micro-organism and some remained alive, and they proceed to point out how it was that such different results were obtained. Before the inoculations were made some of the animals received injections of blood taken from a dog, which a few months previously had been infected with this same microbe, but had recovered. The rabbits which received the dog's blood all survived the inoculations, whilst those which did not, succumbed in every case to the action of the Staphylococcus pyosepticus. So struck were the authors by these remarkable results that they repeated them, and their further investigations fully confirmed those originally obtained, proving that they were not "un fait exceptionnel."

Here we have the first steps in the direction of serum-therapy, that new treatment of disease which during the last few years has been so prominently before the public in the cure of diphtheria, tetanus, and other maladies, and for the development of which we owe so much to the labours of Behring, Roux, Kitasato, and other investigators.

The astounding fact that the blood of animals which have been trained to artificially withstand a particular disease becomes endowed with the power of protecting other animals from that disease is only in the earliest stages of its application. The results, however, which have already been accomplished are of so encouraging a character that the hope is justified that serum-therapy is destined to revolutionise the treatment of disease. One of the latest uses which has been made of this method of combating disease is the employment of serum for the cure of bubonic plague. During the recent outbreak of plague in India, Yersin, formerly a student and assistant at the Paris Pasteur Institute, was despatched to India to superintend the administration of this new remedy, and the serum he employed was that derived from horses which had been subjected to, and had recovered from, inoculations with the plague bacillus. The treatment of snake bites by means of curative serum will be dealt with in more detail later on; it only remains to cite it here as another instance of the success which is attending the new methods of protection against disease.

Another and highly ingenious application of serum has been brought forward by Pfeiffer, Gruber, Widal, and others. This is the so-called sero-diagnosis of disease, and has been employed already with success in the identification of typhoid fever as such. The method sounds simple in the extreme, and consists in taking a few drops of blood from a patient supposed to be suffering from typhoid fever and mixing them with a recent cultivation in broth of genuine typhoid bacilli. If the blood is derived from a typhoid-infected person, then the bacilli should exhibit a curious and characteristic appearance when examined under the microscope. Instead of moving about as individuals in various parts of the microscopic field, they should be seen gathering or clumping together in numerous small heaps, their movements the while becoming paralysed.

The State Board of Health of Massachusetts has recently taken up the official sero-diagnosis of typhoid fever, and issues in response to applications a simple outfit with instructions how to collect specimens of blood and a form which they request shall be returned filled in with all the details concerning the case under observation. Only a few drops of blood are required for the examination, and these before being despatched to the State Laboratory are collected on slips of paper and allowed to dry. If the addition of this suspected blood in the proportion of one to twenty to a young and vigorous culture of typhoid bacilli succeeds in paralysing their movements, producing the characteristic clumping together or agglutination of the bacilli, then the reaction is considered positive and the case one of typhoid fever.

That, however, some risk attends the placing of too implicit a reliance on this method of diagnosis alone is evident from the fact that a negative reaction, or in other words, absence of all agglutinising phenomena, is sometimes associated with blood throughout what is beyond all question a well-defined case of typhoid fever, whilst in the first week of this disease the test is frequently negative in character. Rouget, who has made a very careful inquiry into the value to be attached to the sero-diagnosis of typhoid fever, states that he has found in a large number of examinations of blood derived from undoubted typhoid patients the agglutination phenomena fail altogether; it is, therefore, not surprising that the sero-diagnosis of this disease is still the subject of much discussion and investigation.

An interesting example of how particular serums may be employed for the detection of particular poisons has been furnished by Dr. Calmette. In some districts of India the natives have an ugly custom of wreaking their vengeance on their enemies by poisoning their cattle, and to effect this both expeditiously and secretly they employ subtle poisons which they know can only be detected with great difficulty. Serpent venom is a favourite substance, whilst abrine, a highly toxic vegetable poison, is another. The method adopted for the application of this abrine is highly original, and consists in taking small bits of wood shaped like miniature clubs, so diminutive in size that they can be concealed in the hand. In the head of the club small holes are bored, and tiny pointed rodlets of a hard greyish substance are fitted into them. Armed with these crude instruments, the natives scratch the cattle in several places, and, although but little external sign of injury is to be seen, the rod-points penetrate the skin and are broken off, and the poison is left to work its lethal way through the animals' system. Mr. Hankin forwarded some of these broken-off rod-points to Dr. Calmette for the identification of their composition, and he diagnosed the material employed as abrine in the following original manner. He first introduced some of this rod material into animals, and found that their symptoms were suggestive of abrine poisoning. To confirm his suspicions, however, he took some more of this rod material, and, before inoculating it into animals, he mixed it with serum derived from animals which had been artificially rendered immune to abrine poison. Instead of the animals into which this mixture of serum and "rod material" had been introduced dying like the previous ones, they remained alive. Had the "rod material" consisted of some poison other than abrine, the abrine serum would not, according to Dr. Calmette, have negatived its action, and it has thus been indicated how protective serums may be successfully employed for the detection of poisons.

Foremost, however, among the beneficent reforms which have followed in the wake of bacteriology must be placed the antiseptic treatment of wounds, or Listerism, as it is now universally designated in recognition of its renowned champion, the former President of the Royal Society. "Lister comprend," in the words of Dr. Roux, "que les complications des plaies sont dues aux germes microbiens venus du dehors et il imagine les pansements antiseptiques. Avec l'antiseptie commencent les temps nouveaux de la chirurgie." It only remains to add that, with the modesty characteristic of a great man, its brilliant author delights in repeating how any good which he may have been permitted to do he owes entirely to the inspiration which he received from the labours of Louis Pasteur.

But if the Victorian era has been productive of so many important applications of bacteriology to commerce and medicine, this period has been also fraught with results of the highest moment in the progress of hygiene.

The terms of intimacy, so to speak, which we have been now able to establish with bacteria has enabled us to discover details of their life and habits which before were shrouded in mystery. Their distribution in air has led to renewed endeavours on the part of sanitary authorities to procure efficient ventilation in our hospitals and public institutions; dust has acquired a fresh horror since it has been shown how disease germs may be disseminated by its means; whilst the important part which flies and lice may play in the spread of epidemics has opened up a new field for research, and made us conscious of a fresh source of danger in our daily life.

The general public, however, is hardly yet fully alive to the capacity for mischief possessed and exercised by the common house-fly. True, it is universally execrated and regarded as a tiresome attendant upon the summer months, but it is not usually considered in any more serious light. That however, the comparative indulgence with which this homely insect pest has been treated is decidedly misplaced and fraught with danger to health, the researches of numerous scientists have now conclusively proved.

As long ago as the year 1888 Professor Celli showed that the germs of consumption, anthrax, and typhoid fever could pass through the digestive organs of flies and reappear in the excreta of the latter not only alive but in full possession of their disease-producing powers. Dr. Sawtschenko made similar experiments with cholera germs. Healthy flies were placed under glass shades and fed with broth in which these micro-organisms were growing, and the latter were not only subsequently recovered from the digestive organs of the flies but also from their excreta in a living and virulent condition.

This is, however, not the only means whereby these insects can distribute deadly and other microbes, for it has been shown that in crawling over substances containing bacteria these may become attached to the feet of flies, and are in this manner transferred to other materials upon which they may alight, just as Pasteur showed many years earlier silkworms can communicate the fatal plague of pébrine by crawling over each other's bodies, carrying in their disease-laden feet the infection from one worm to another. During the recent outbreak of bubonic plague in the East the part played by flies in disseminating the virus has been repeatedly emphasised. Yersin was the first who called attention to the presence in large numbers of virulent plague bacilli within the bodies of flies which he collected in the vicinity of plague-stricken persons, and it was found that flies which had fed on plague-infected material and were then isolated lived for several days afterwards, during which time virulent plague bacilli were present in their bodies in immense numbers; thus were these insects converted into winged messengers of evil of the most repulsive type.

I am not aware whether any experiments on the vitality and transmissibility of diphtheria and consumption germs by means of flies have been made; but in view of the overwhelming evidence of the culpability of these insects in spreading plague, it is not unreasonable to presume a responsibility on their behalf in regard to other diseases; indeed, in the report issued by the Army Medical Commissioners of the Spanish-American War, it is emphatically stated that flies played an important part in the dissemination of typhoid fever.

There is no question as to the capability of certain micro-organisms to reside for considerable periods of time within the bodies of flies, and during this sojourn to abate no jot of their virulence. Indeed, it has been shown that the bodies of these insects may constitute incubators of a most successful type, for some varieties of bacteria grow luxuriantly and multiply abundantly within them.

In the hot days of summer, when flies abound, it would be well to banish these insects, as far as lies in our power, not only from our sick-rooms in particular, but from our general surroundings. The catholic taste of flies for garbage of all kinds is too well known to require entering into, but the consequences which may follow from their visits to dustbins and centres of disease, and then alighting upon our food or persons, has received too little attention in the past.

In regard to the subject of insects as disease disseminators, it may be mentioned that Mr. Hankin, when studying plague conditions in India, expressed his belief that ants in Bombay also assisted in spreading the scourge, for he found that when he inoculated mice with the excreta of ants, such insects having previously fed on plague-stricken rats, the mice succumbed to plague in a few hours. Fleas have also been conclusively proved to be carriers of plague germs.

There is no doubt that the revelations of hygienic science have aroused the vigilance and zeal of public authorities in various new directions to try and cope with the spread of zymotic disease.

In no direction, perhaps, is the fruit of this energy so apparent as in the increasing supervision which it has incited over two of the greatest menaces to public health which hang over society —i. e. our water and dairy supplies. Now that it has been proven beyond doubt that the germs of consumption, typhoid fever, and cholera can be and are distributed through the consumption of contaminated milk or water, not to mention other diseases such as diphtheria and scarlet fever, an ever-increasing demand is being made that these all-important articles of diet shall be protected from pollution, and that public authorities shall be made responsible for their distribution in a pure and wholesome condition.

It is, however, undoubtedly in the matter of water that the greatest service has been rendered by bacteriology to sanitary science, and for the important advance in this department we are indebted to the beautifully simple and ingenious methods devised by Robert Koch.

Not yet twenty years have passed since the new bacterial examination of water was introduced and systematically employed, and the use which has been made of the opportunities thus opened up of investigating water problems on an entirely new basis is shown by the voluminous dimensions which the literature on this one branch of bacteriology alone has reached. Considerably upwards of two hundred different water bacteria have been isolated, studied, and their distinctive characters chronicled. The behaviour of typhoid, cholera, and other disease-producing microbes in waters of various kinds has been made the subject of exhaustive experiments; the purification power of time-honoured processes in operation at waterworks and elsewhere has been for the first time accurately estimated. Water engineers have through these bacteriological researches been provided with a code of conduct drawn up by the light of erudite scientific inquiries, which has now rendered possible the removal of the process of water purification from the rule of empiricism guided by tradition, and to raise it to the level of an intelligent and scientific undertaking.

The above short sketch may serve to convey some idea of the rise and phenomenal development of bacteriology during the past sixty years. To record, even in outline, the individual triumphs of the various branches of this science would require volumes, whilst the astounding mass of work already accumulated by its devotees is but the earnest, the guarantee of yet greater achievements in the future.

The progress which has been made in this brief period of time must not necessarily be expected to continue at this rapid rate; it may be that generations to come have yet the hardest and the longest tasks to accomplish; for in science, as in other walks of life, it is, as a rule, the easiest problems, which are first disposed of, and the farther we advance the more complicated, the more intricate become the questions to be attacked, the difficulties to be overcome.

The late Queen's reign has bestowed a splendid legacy of bacteriological discoveries upon those who, in the future as in the present, must inevitably follow in the footsteps of those great and brilliant leaders of bacteriological science belonging to this auspicious era, Louis Pasteur and Robert Koch.