226 



SCIENCE. 



[Vol. XX. No 507 



more overwhelming the effect ! We thus have an explanation of 

 the fact often observed that at the beginning of some epidemics, 

 especialiy of such grave maladies as yellow-fever, typhus, Asiatic 

 cholera, etc., the victims seized by them frequently die within 

 less than an hour after the first symptom has indicated the out- 

 break of the disease. 



How difficult, however, bacteriological investigations are may 

 be judged from the following data. Some of the pathogenic 

 bacteria resemble each other so greatly that the microscope alone, 

 however powerful, does not suffice for their recognition. In such 

 cases the suspicious microbes are exposed to the influence of 

 various coloring processes; and, as each species evinces a behavior 

 different from that of another variety, the result of the coloring 

 tests often leads to the recognition of the species. But even that 

 does not satisfy the modern bacteriologist. Pure-culture and ex- 

 perimental research must be added. After all the microbes 

 present in a diseased tissue have been removed, they are spread 

 over a layer of beef-tea gelatine, where their development is 

 watched under the microscope. If there are several species — sup- 

 pose three, though there may be many more — it is soon found that 

 on three different spots of the gelatine certain changes are going 

 on. While in one spot a peculiar excrescence has formed, in 

 another a cup-shaped depression is noticed with the gelatine near 

 it dried, and in the third the shape observed is still different and 

 the gelatine surrounding this spot has become more fluid. From 

 these various behaviors the expert can probably recognize which 

 of the three species is the pathogenic one for whioh he is looking. 

 Certainly in all these researches care must be taken that no other 

 micro-organism can enter the receptacle in which the develop- 

 ments are progressing; and, as the atmosphere constantly con- 

 tains many kinds of microbes, the reader may have some concep- 

 tion of the difiiculties presenting themselves. 



After the suspicious species has been recognized on the gelatine 

 soil, a minute particle is taken from that particular spot, and car- 

 ried to another culture-soil, which may again be some bouillon 

 gelatine, or agar-agar, or a potatoe-skin, or blood-serum, or any 

 similar substance. It may also be noted that the different species 

 evince a natural preference for some soil, while they obtain only 

 a stunted growth in others. 



In all these processes every instrument used must be aseptic, 

 i.e., free from bacteria. Under the precautions mentioned the 

 development of the micro-organisms selected from the one spot 

 and transferred to a special culture-soil is again carefully noted, 

 and if the phenomena accompanying the multiplication and 

 maturing in this pure culture correspond with those known as 

 characteristic of the species in question — in the case of an unknown 

 species these characteristics must first be elucidated by special 

 observations — then the experimental stage is entered. A minute 

 particle of the result of the last pure culture is introduced into 

 some animal organism, and if there it gives rise to the lesions and 

 symptoms of the same infectious disease as that in which the 

 bacteria had first been met with, and if later the specific bacteria 

 taken from the blood or tissues of the inoculated and infected 

 animal again behave under pure culture as the original species 

 did, the proof is considered final and complete, and the microbe 

 in question is recognized as the pathogenic element of the particu- 

 lar infectious disease in which it was found. 



To illustrate, the sputum of patients suffering from tubercular 

 consumption contains other bacteria besides the tubercle bacilli — 

 the real cause of the fatal malady. A microscopical examination 

 even with the application of some color-tests, while for practical 

 purposes easily concluded and sufficient, if necessary to be done 

 with scientific exactness does not answer every demand ; because 

 the species causing glanders, the fatal disease of horses, that of 

 tubercle, of anthrax, and of cholera, at some time or other, have 

 nearly the same shape. One appears a little thicker, another 

 more rounded at one point, a third slightly longer; but, if we re- 

 member their minute size, we may imagine how slight the differ- 

 ence must be when one is an immeasurable bit smaller or thicker. 

 In this instance other color-tests aid the expert; for, while the 

 bacilli of glanders take on the coloring without difHculty, those 

 of tubercle and of anthrax have to be exposed to its influence a con- 

 siderable time. Then the bacilli of anthrax, after the staining, 



easily yield the color to the influence of acids, but those of tubercle 

 resist the action even of sulphuric acid, while the comma bacilli 

 of cholera soon develop other peculiar characteristics. 



Sputa containing the tubercle bacilli were dried, mixed with 

 street-dirt, exposed for months to all kinds of weather, again 

 dried, and flnally used for the following purpose. Two small 

 brick houses were erected in Paris some miles apart, and into each 

 one dozen healthy rabbits — A and B — were placed, which all 

 received the same food, water, treatment, and attention with this 

 difference: into the building containing the rabbits A some of the 

 sputum dust referred to was thrown daily for a week by the aid 

 of a pair of bellows, so as to mix with the air in the room. About 

 six weeks later all these rabbits had died of galloping consumption, 

 while the rabbits B remained in excellent health. 



A bacteriological examination showed the presence of the tuber- 

 cle bacilli in large numbers in the tissues of the dead rabbits. 

 Some of these bacteria, taken for pure culture, were later again 

 introduced into the tissues of other aniiuals, and again caused the 

 outbreak of consumption in them and their final death. 



The specific microbes of a great number of infectious diseases 

 have been discovered, while in others the investigations are still 

 being carried on. For the purpose of diagnosis this discovery is 

 of the utmost import, as the presence of the specific microbes in 

 any disease at once determines the true nature of the latter. 

 Then by a careful study of the conditions of development of these 

 bacteria valuable information has been gained, which has proved 

 useful for the purposes of prevention. Thus in consumption we 

 know, if the sputa of tuberculous patients are destroyed, and if 

 the milk and flesh of animals suspected to be afflicted with the 

 disease are thoroughly boiled! that the danger of infection from 

 them disappears. In the same way we have learned that the germs 

 of cholera are not propagated by the atmosphere, but that they 

 must be swallowed to penetrate into the intestines where alone 

 they can mature, multiply, and produce the disease. The 

 knowledge of these facts enables us to prevent the spreading of 

 the epidemic. 



A study of the behavior of the bacteria of decomposition has 

 led to the application of modern asepsis in surgery. A wound 

 that is thoroughly impregnated with a disinfectant, i.e., with a 

 remedy which destroys all such microbes, need only be protected 

 against further contamination to insure its healing by first inten- 

 tion, meaning without the development of pus. Many serious 

 operations which were indicated and which would have saved life 

 years ago, while not presenting in their execution special difficul- 

 ties to the experienced surgeon, could not be performed because 

 the immense pus-discharge which would have followed them 

 would have proved exhausting, and have brought about the death 

 of the patient. Thus it was with operations on large joints, with 

 injuries affecting the abdominal organs, and with lesions of some 

 of the serous membranes, as the pleura, etc. To-day these opera- 

 tions are performed under the strictest aseptic precautions; the 

 hands of the operator and those of his assistants, every instrument 

 and appliance to be used, the external surface above the seat of 

 the parts to be operated upon — all are disinfected and kept fx-ee 

 from bacteria. The operation ended and the bleeding arteries 

 secured with aseptic catgut, which is later absorbed, the parts 

 concerned are completely disinfected and the dressing applied, 

 which, impregnated with material that would prove destructive 

 to any micro-organism entering it, is also calculated to exclude 

 the atmosphere. The result is surprising. In many of the most 

 serious operations, those on the brain included, the dressing often 

 is not renewed but allowed to remain for a week or longer, and 

 when finally taken off the parts underneath are found to have 

 healed without a drop of pus having ever been present and with- 

 out the temperature of the patient having ever ascended above 

 normal, thus demonstrating the absence of all wound-fever, once 

 so dreaded. Hospital gangrene, erysipelas, and puerpural-fever 

 to-day are almost unknown. And this remarkable achievement 

 is due solely to the results of bacteriological studies I 



At the present time the most prominent investigators, the cele- 

 brated Koch in Berlin at their head, are endeavoring to find the 

 proper remedies with which to antagonize the action of patho- 

 genic bacteria. They are trying to discover a ptomaine which 



