AVIAN TUBERCULOSIS. 245 



differences, and, reasoning from analogy, we might infer 

 that probably the human subject also would be little 

 susceptible to infection from avian tuberculosis. The 

 question remains, are these differences of a permanent 

 character? Now it has been found that occasionally the 

 inoculation of fowls with tubercle bacilli from the human 

 subject produces tuberculosis, and that, when this occurs, 

 the disease can be readily transmitted to other fowls. 

 Also in some cases, inoculation with avian tubercle bacilli 

 produces ordinary tubercle nodules in guinea-pigs and 

 rabbits (Courmont and Dor), and, in other cases, these 

 lesions are found after the bacilli have been passed through 

 the tissues of a number of guinea-pigs. The matter seems 

 permanently settled by the experiments of Nocard, in which 

 mammalian tubercle bacilli have been made to acquire all 

 the characters of those of avian origin. The method 

 adopted was to place bacilli from human tuberculosis in 

 small collodion sacs containing bouillon and then to insert 

 each sac in the peritoneal cavity of a fowl. The sacs were 

 left in situ for periods of four to eight months. They were 

 then removed, cultures were made from their contents, 

 fresh sacs were inoculated and introduced into other fowls. 

 In these conditions the bacilli are subjected only to the 

 tissue juices, the wall of the sac being impervious both to 

 bacilli and to leucocytes, etc. After one sojourn of this 

 kind, and still more so after two, the bacilli are found to 

 have acquired some of the characters of avian tubercle 

 bacilli, but are still non-virulent to fowls. After the third 

 sojourn, however, they have acquired this property and pro- 

 duce in fowls the same lesion as bacilli derived from avian 

 tuberculosis. It therefore appears that the bacilli of avian 

 tuberculosis are not a distinct and permanent species, but 

 a variety which has been modified by growth in the tissues 

 of the bird. Evidently also there are degrees of this 

 modification, according to the period of time during which 

 the bacilli have passed from bird to bird. We may add 

 that tuberculin prepared from avian tubercle bacilli has the 

 same action as the ordinary tuberculin. 



