VARIETIES OF TUBERCULOSIS 277 



from the two classes of animals show important 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 1 The matter seems conclusively 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 (v. p. 144) containing bouillon, 

 and then to insert each sac in the peritoneal cavity of a fowl. 

 The sacs were left in situ for periods of from four to eight 

 months. They were then removed, cultures were made from 

 their contents, fresh sacs were inoculated from these cultures 

 and introduced into other fowls. In such 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 produce 

 in fowls the same lesions as bacilli derived from avian tuber- 

 culosis. It therefore appears that the bacilli of avian tuber- 

 culosis are not a distinct and permanent species, but a variety 

 which has been modified by growth in the tissues of the bird. 

 It is also interesting to note that Rabinowitch has cultivated 

 tubercle bacilli of the mammalian type from some cases of tuber- 

 culosis in parrots kept in confinement. 



3. Tuberculosis in the Fish. Bataillon, Dubard, and Terre 

 cultivated from a tubercle-like disease in a carp, a bacillus 

 which, in staining reaction and microscopic characters, closely 

 agrees with the tubercle bacillus. The lesion with which it 

 was associated was an abundant growth of granulation tissue in 

 which numerous giant-cells were present. It forms, however, 

 luxuriant growth at the room temperature, the growth, being 

 thick and moist like that of avian tubercle bacilli (Fig. 84, c). 

 Growth does not occur at the body temperature, though by 

 gradual acclimatisation a small amount of growth has been 

 obtained up to 36 C. Furthermore, the organism appears to 

 undergo no multiplication when injected into the tissues of 

 mammals, and attempts to modify this characteristic have so 

 far been unsuccessful. Weber and Taute have cultivated this 

 organism from mud, and also from organs of healthy frogs. It 

 is thus probably to be regarded as a saprophyte which is only 

 occasionally associated with disease in the fish. According to 



