73 



there suddenly appears in the iris a greater or less num- 

 ber of very minute gray tubercles which, precisely like 

 the human tubercles, grow to a certain size, then become 

 caseous, etc. In rabbits Salomonsen and I observed 

 the eruption of the tubercles usually about the twenty- 

 first day after the inoculation, in guinea-pigs a week 

 earlier as a rule." "Yet these observations have first 

 acquired their full significance from the fact that the 

 tuberculosis is generated by the inoculation of tubercu- 

 lous matter only and of nothing else? These are the 

 words of a man who, some years ago, was inclined to 

 the belief, from the fact that the disease may follow sub- 

 cutaneous or intraperitoneal mechanical irritation, that 

 tuberculosis was not an etiologically specific disease. In 

 his " Allgemeine Pathologic," in discussing the same 

 subject, Cohnheim says, " After a few days the cornea 

 is quite clear, the iris thoroughly clean and in perfectly 

 normal condition ; in the aqueous humor there is also no 

 exudate to be seen, so that one can see the piece intro- 

 duced sharply and clearly defined against the lens cap- 

 sule ; and thus it remains unchanged for weeks, except 

 perhaps that the particle becomes somewhat smaller. 

 All at once, in our cases between the twentieth and thir- 

 tieth day, the scene changes ; there arises in the iris 

 tissue a considerable number of small transparent gray- 

 ish tubercles." " Yet the most interesting feature is that 

 in numerous instances, though not always, a more or 

 less extensive tuberculosis of lungs, lymph-glands, spleen, 

 and other organs, occurs. From these experiments it 

 cannot be doubted, first, that the tuberculosis by inocu- 

 lation can develop without the medium of a coagulated 

 exudate, and, second, that it has a stage of incubation." 

 He says further, " Where experiments so positive and so 

 easy of repetition are adduced, it would seem impossible 

 to discuss any longer the question of infectiousness." 



Until, therefore, we can otherwise explain the fact 



that general tuberculosis can be induced by mixing small 



quantities of tuberculous matter (but not by mixing any 



other tissue) with food ; by simple inhalation of phthisical 



4 



