270 BACILLI PATHOGENIC IN MAN. 



rats, and white mice were placed. The animals were 

 then kept in a special cage and well tended ; after 28 

 days they were killed, and all showed extensive tuber- 

 culosis. 



The inoculations were made on a total of 217 animals. 

 The more susceptible animals guinea-pigs, field mice, 

 rabbits, and cats died as the result of all the different 

 modes of infection ; and where large numbers of bacilli 

 were employed, dogs, rats, and white mice were also un- 

 able to withstand their action. 



Control It must also be mentioned that numerous control ex- 



periments were made with a great variety of cultivations 

 and mixtures of other bacteria, and that the inhalation 

 experiments were also controlled by Koch in a similar 

 manner. Nevertheless, in no case was tubercular 

 disease observed in these animals. 



The proof that we must look on the tubercle bacillus 

 as the only and all-sufficient cause of all kinds of tuber- 

 cular diseases has thus been brought by Koch with a 

 completeness and certainty which has scarcely ever been 

 attained as regards the etiology of any other disease. 

 The results of Koch's experiments have been subse- 

 quently confirmed completely by several observers ; thus 

 the whole series of investigations has been repeated by 

 Watson Cheyne, Rosenbach, the author, &c. The 

 constant and exclusive occurrence of the tubercle bacilli 

 in tubercular diseases has been confirmed by numerous 

 observers, more particularly their occurrence in 

 phthisical sputum, and also in the surgical tubercular 

 affections in lupus, bovine tuberculosis, &c. The 

 objections which have been raised by Formad, Spin a, 

 and others, against the etiological significance of the 

 tubercle bacillus, or against certain parts of the proof 

 furnished by Koch for example, against the specific 

 applicability of the methods of staining, against the ex- 

 periments on animals, &c. have been shown to be 

 badly founded in every respect, and have for the most 

 part arisen only from imperfect employment of Koch's 

 methods. 



