Microbic Diseases Individually Considered. 231 



pected from their physical characters to be of a tuber- 

 cular nature. 



In the case of young, gray tubercles it suffices to 

 spread upon a cover glass the product obtained by 

 scraping their cut surface : the bacilli are here uni- 

 formly distributed. But when the tubercles are al- 

 ready caseated the caseous matter frequently contains 

 but few bacilli except in birds, where, on the contrary, 

 they are very numerous ; this substance is first re- 

 moved and the bacilli sought for in the wall of the 

 caseous tubercle. The same method may be employed 

 for cavities although these often contain a liquid very 

 rich in bacilli. 



Experimental inoculations. — Tuberculosis is inocula- 

 ble to the horse, ass, ox, sheep, pig, dog, cat, rabbit, 

 guinea pig, and to fowls. 



Subcutaneous inoculation is without effect in the 

 horse, ass, sheep, pig, dog, cat, and chicken. 



Ingestion of virulent substances produces the dis- 

 ease, but not in all cases, in the horse, sheep, pig, dog, 

 and cat. Cattle are easily tuberculized in this way. 

 The chicken remains unaffected when sputa or tuber- 

 cular products of mammals are mixed with its food. 



Intravenous injection gives much surer results. 

 Except in the case of birds it is almost invariably fol- 

 lowed by a generalized tuberculosis of the lung with 

 possible extension to other organs. In the ass the 

 experiments of M. Chauveau have shown that these pul- 

 monary granula heal spontaneously after a few weeks. 

 Fowls do not usually contract the tuberculosis of 

 mammals by way of the circulation. Thus, MM. 

 Cadiot, Gilbert, and Roger have recently announced 

 that out of forty pullets inoculated by them either in 



