340 TUBERCULOSIS AS A TYPE OF BACTERIAL DISEASE 



The evidence furnished by Dr Koch for the conclusion that human tuberculosis is 

 not communicable to animals is briefly this : Nineteen young cattle which had 

 stood the tuberculin test (and were therefore presumably free from tuberculosis) 

 were treated as follows : Six were fed with tubercular human sputum almost daily 

 for seven or eight months. Four repeatedly inhaled great quantities of bacilli 

 which were distributed in water and scattered with it in the form of spray. The 

 remainder (9) were infected in various ways with pure cultures of tubercle bacilli 

 taken from human tuberculosis, or tubercular sputum direct from consumptive 

 patients. In some cases the bacilli or sputum were injected under the skin, in 

 others into the peritoneal cavity, and in others into the jugular vein. None of 

 these 19 cattle showed any symptoms of disease. After six to eight months they 

 were killed, and in their internal organs not a trace of tuberculosis was found. The 

 result was utterly different, however, when the same experiment was made on 

 cattle free from tuberculosis with tubercle bacilli from bovine sources. In this 

 case virulent tuberculosis rapidly supervened. Further, an almost equally striking 

 distinction between human and bovine tuberculosis was brought to light by a 

 feeding experiment with swine. Six young swine were fed daily for three months 

 with the tubercular sputum of consumptive patients. Six other swine received 

 bacilli of bovine tuberculosis with their food daily for the same period. The 

 animals that were fed with sputum remained healthy and grew lustily, whereas 

 those that were fed with the bacilli of bovine tuberculosis soon became sickly, were 

 stunted in their growth, and half of them died. After three months and a half the 

 surviving swine were all killed and examined. Among the animals that had been 

 fed with sputum no trace of tuberculosis was found, except here and there little 

 nodules in the lymphatic glands of the neck, and in one case a few gray nodules in 

 the lungs. The animals, on the other hand, which had eaten bacilli of bovine 

 tuberculosis had, without exception (just as in the cattle experiment), severe 

 tubercular diseases, especially tubercular infiltration of the greatly enlarged 

 lymphatic glands of the neck and of the mesenteric glands, and also extensive 

 tuberculosis of the lungs and the spleen. The difference between human and 

 bovine tuberculosis appeared not less strikingly in a similar experiment with asses, 

 sheep, and goats, into whose vascular systems the two kinds of tubercle bacilli 

 were injected. Dr Koch also stated that other experiments in former times, and 

 recently in America, have led to the same result. 



In support of his second contention, namely, that bovine tuberculosis is not trans- 

 missible to man, Dr Koch points out that the direct experiment upon human beings 

 is, of course, out of the question, and hence it is necessary to rely upon indirect 

 evidence. Dr Koch, therefore, reasons as follows : Tuberculosis, caused by meat 

 or milk, can be assumed with certainty only when the intestine suffers first, i.e., 

 when a so-called "primary tuberculosis" of the intestine is found. If bovine 

 tubercle bacilli are capable of causing disease in man there are abundant oppor- 

 tunities for the transference of the bacilli from one species to the other, and cases 

 of primary intestinal tuberculosis from consumption of tuberculous milk ought 

 therefore to be of common occurrence. " But such cases," he maintains, " are 

 extremely rare." In support of this view Dr Koch stated that he had only seen 

 2 cases ; that only 10 cases had been met with in the Charite Hospital in 

 Berlin ; and that out of 3104 post-mortems of tubercular children, Biedert observed 

 only 16 cases. Reference was also made to other similar evidence. 



Finally, Dr Koch maintained that ** though the important question whether man 

 is susceptible to bovine tuberculosis at all is not yet absolutely decided, and will not 

 admit of absolute decision to-day or to-morrow,' one is, nevertheless, already at 

 liberty to say that if such a susceptibility really exists the infection of human beings 

 is but a very rare occurrence. " 



Such, then, was the position of the question at the end of 1901. It may be con- 

 venient here to add the chief reasons for supposing that bovine and human 

 tuberculosis are one and the same disease, and intercommunicable : 



1. That the tubercle bacillus of bovine tuberculosis possesses characteristics of 

 shape, size, staining, and cultivation on artificial media similar to, and in the 

 opinion of many authorities almost identical with, the tubercle bacillus of human 

 origin. 



