KOCH'S EXPERIMENTS 225 



bacillus in the two species differed in various respects as to 

 morphological, biological, and pathological properties (Theobald 

 Smith, Dinv.iddie, Frothingham). In 1901, however, Dr Koch 

 expressed the opinion that "human tuberculosis differs from 

 bovine, and cannot be transmitted to cattle,"^ and that bovine 

 tuberculosis was scarcely, if at all, transmissible to man. On the 

 same occasion counter evidence was produced by McFadyean,* 

 Ravenel.^ Crookshank,^ and many others. Various experiments 

 are now in process of being carried out to elucidate this ques- 

 tion, including Government commissions in Great Britain and 

 Germany. 



The evidence furnished by Dr Koch for the conclusion that 

 human tuberculosis is not communicable to animals was 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 (nine) were infected in various 

 ways with pure cultures of tubercle bacilli taken from human tuber- 

 culosis, 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 nineteen 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 entirely different, however, when the same experiment was 

 made on cattle free from tuberculosis with tubercle bacilli from 

 boz'ine sources. In this case virulent tuberculosis rapidly supers 

 vened. 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 



' Trans. British Congress on Tuberculosis, 1901, vol. i., p. 29. 



2 Ibid., vol. i., p. 79. 



' Ibid., vol. i., p. 91, and vol. iii., p. 553. 



* Ibid., vol. i., p. 92. 



P 



