288 TUBERCULOSIS 



place and that the characters of the type are comparatively 

 stable. The question is still an open one, and it is doubtful 

 whether or not a bovine type after long sojourn in the human 

 tissues will assume the characters of the human type ; if it does, 

 the proportion of cases actually due to the bovine type will be of 

 course larger than is indicated by the characters of the organism 

 obtained from the lesion. It is quite likely that, although the 

 bovine bacilli are more virulent to the lower animals than the 

 human bacilli are, this does not also hold in the case of 

 the human subject. In fact, the comparative chronicity of the 

 primary abdominal lesions in children, in the first instance, 

 would point rather to a low order of virulence towards the human 

 subject. We may also add that there are cases, notably those 

 of Ravenel, in which accidental inoculation of the human 

 subject with bovine tubercle has resulted in the production of 

 tuberculosis. 



Some other facts obtained by the Royal Commission may be given. 

 The bovine type of bacillus alone was found in the sheep, goat, and horse, 

 whilst in the pig the bovine type was found in the great majority of 

 cases, though in some the human type, and in others the avian tubercle 

 bacillus, was present. In the case of these two latter the lesions were of 

 a more localised kind. The bovine type was also found in the cat. 

 The human type was found in animals in confinement, e.g., the antelope, 

 gnu, chimpanzee, and macacus rhoesus, and also in the parrot. The 

 animals most susceptible to inoculation with the human type are the 

 guinea-pig, rhoesus, and chimpanzee ; the dog, rat, and mouse are 

 practically immune, while the calf, rabbit, pig, and goat occupy an 

 intermediate position. The parrot also has been found to be susceptible 

 to inoculation with the human type. It was also found that when cows 

 were inoculated subcutaneously with considerable quantities of bacilli 

 either of the human or bovine type the bacilli were excreted in the 

 milk, and that in these cases the udder appeared normal. There is 

 therefore the presumption that when during the course of the disease 

 the bacilli are present in the blood stream, they may make the milk 

 infective even though there are no lesions in the udder. 



2. Avian Tuberculosis. In the tubercular lesions in birds 

 there are found bacilli which correspond in their staining re- 

 actions and in their morphological characters with those in 

 mammals, but differences are observed in cultures, and also on 

 experimental inoculation. These differences were first described 

 by Maffucci and by Rivolta, but special attention was drawn to 

 the subject by a paper read by Koch at the International Medical 

 Congress in 1890. Koch stated that he had failed to change 

 the one variety of tubercle bacillus into the other, though he did 

 not conclude therefrom that they were quite distinct species. 

 The following points of difference may be noted : 



