

SCIENC 



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A WEEKLY NEWSPAPER OF ALL THE ARTS AND SCIENCES. 



Eighth Yeah. 

 Vol. XVI. No. 399. 



NEW YORK, September 36, 1890. 



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 3.50 Pee Year, in Advance. 



KOCH ON BACTERIOLOGY. 



The Lancet of Aug. 16, 1890, gives a summary of the address of 

 Koch at the Tenth International Medical Congress, in which he 

 declared that he had not much that was new to tell, but he would 

 make a preliminary communication regarding the result of impor- 

 tant new experiments. This communication, a resume, of which 

 is published in the Medical and Surgical Beporter, had reference 

 to a remedy for consumption discovered by him, which, however, 

 he would not name till his experiments were ended. The rest of 

 his address was an admirably clear account of the progress of 

 bacteriological research. 



Only fifteen years ago one regarded the micro-organisms occa- 

 sionally observed in the bodies of diseased animals and persons 

 more as curiosities than as things essentiallj' connected with the 

 disease; and, considering the .areat ignorance of their nature which 

 then prevailed, (his could not but be so. There were investigators, 

 for instance, who declared bacteria to be crystalloid bodies, not 

 living organisms. With the perfecting of the magnifying instru- 

 ments, tlie applica'ion of staining, the propagation of organisms 

 on nutritive media, culminating soon in pure cultivation, a rapid 

 change took place. It became possible to distinguish a number of 

 quite definite sorts with certainty, and to ascertain that they vv-ere 

 distinctly connected with the diseases in which they were found. 

 It was further ascertained that one sort of bacteria was not trans- 

 formed into another; and the remarks of old writers on leprosy 

 and consumption, for instance, even justified the conclusion, that 

 just as certain diseases, presumably caused by micro-organisms, 

 had remained unchanged, their germs also must, on tlie whole, 

 have retained their old qualities. Within certain limits, indeed, 

 deviations of demeanor had been observed in some bacteria, but 

 that was the ca^e among the higher plants too, without the vari- 

 eties ceasing to belong to the sx^ecies. The main gain of this 

 period of research was the recognition of the fact that the thing 

 was to discover as many morphological and biological qualities of 

 a bacterium as possible, so as to be guarded against the danger of 

 confounding various bacteria. There v\'as still a danger of this 

 with certain bacteria. — the typhus and diphtheria bacilli, forexam- 

 ule, — whereas it bad been removed in the case of the tubercle and 

 cholera bacilli by the very exact investigations of these organisms. 

 In their case too, however, the bacillus must never be determined 

 by one mark alone. He had experienced this in his own case, 

 having for some time taken the bacillus of chicken cholera — for 

 the special study of which he had not had material — for a variety 

 of the bacillus of Asiatic cholera, till a new series of experiments 

 had convinced him of his error. Whether the germ of chicken 

 cholera would have an injurious effect on human beings was still 

 a question, and a question that would not easily be answered, as 

 one could not well make direct experiments on human beings, but 

 must wait to see whether the bacillus of chicken cholera would 

 not one day appear in a human cholera jaatient. 



As to the etiological connection of the noxious bacteria with 

 infectious diseases, general opinion was at first against it, and 

 strict proof was necessary. It was necessary to prove in all cases 

 that the disease and the micro-organism always appear to- 

 gether; that the micro-organism in question does not appear in 

 any other disease; and that the micro organism, propagated out- 

 side of the body through several generations, always produces the 



same disease if it gets into the body again. Now that the etio- 

 logical connection had been proved in this manner in anthrax, 

 tuberculosis, and erysipelas, and the resistance of opponents 

 broken, one might confine one's self in further cases to the two 

 first lines of proof. This proof had still to be given in the case of 

 abdominal typhus, ague, leprosy, diphtheria, and Asiatic cholei-a; 

 but in the case of the latter it was already generally assumed that 

 the cholera bacillus was the cause of cholera. As subjects of in- 

 vestigation for the immediate future, Koch designated the ques- 

 tion whether the pathogenic bacteria live only in the body, or 

 outside of it too, and in the latter case only occasionally get into 

 the body and cause disease; also the manner of getting into the 

 body and their demeanor there. 



The next advance in bacteriology was the discovery of the poi- 

 sons excreted by the bacteria, which were now regarded as the 

 cause of death in fatal bacterial diseases, for the opinion that the 

 white blood- corpuscles resist the bactei'ia was more and more 

 losing ground. Koch then discussed the spore-formation of some 

 bacteria, and the influences of air, warmth, moisture, and chemi- 

 cals on bacteria. Direct sunlight quickly killed bacteria; the tu- 

 bercle bacillus, for instance. Even daylight produces the same 

 effect, though more slowly. Cultivations of the tubercle bacillus, 

 propagated for from five to seven days at a window, died. Moist- 

 ure was necessary for the growth of bacteria; moisture, how- 

 ever, on the other hand, hindered their spreading. A bacterium 

 never rose: its transmission took place only by the flying of dust, 

 if it remained for some time capable of life in dry air. By means 

 of improved staining methods some knowledge of the inner struc- 

 ture of bacteria had recently been gained. There seemed to be 

 an inner nucleus of plasma with flagella proceeding from it. In 

 certain infectious diseases — measles, scarlet-fever, and small-pox, 

 for instance— the presence of a pathogenic bacterium had not yet 

 been proved. In hydrophobia, influenza, whooping-cough, tra- 

 choma, yellow-fever, cattle-plague, and pleuro-pneumonia of 

 cattle, also, no specific bacterium had been discovered, though the 

 infectious nature of these diseases was evident. And perhaps 

 these diseases were caused, not by bacteria, but by organic para- 

 sites belonging to quite another group of animated beings. In the 

 blood of malaria patients protozoa had been found, which were 

 now suspected of causing this and other infectious diseases. 

 Whether protozoa, the lowest representatives of the animal world, 

 really deserved this suspicion, would have to be decided by a 

 method analogous to bacteriological pure cultivation. 



But now there remained the question as to what had been the 

 practical utility of all these extremely laborious investigations. 

 The investigator indeed, ought not to inquire after the iiumediate 

 practical utility of his work. In the present case, however, the 

 question was not entirely devoid of justification. Nor was it quite 

 impossible to give it a satisfactory answer. Had not bacteriologi- 

 cal investigation alone led to effective methods of disinfection? 

 The value of water-filtration, the question of the filtering qualities 

 of the soil, of the fitness of surface water for use as drinking- 

 water, of the best method of constructing wells, the sterilization 

 of milk (so important especially for the nutrition of infants), the 

 investigation of the air in schoolrooms and in sewers, the proof of 

 the presence of pathogenic bacteria in the .soil and in the air, were 

 all bacteriological questions or conquests. 



The diagnosis of isolated cases of Asiatic cholera rendered 



