282 TUBEKCULOSIS 



Commission, are that this modification does not take 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 eases, 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 maeacus rhcesus, and also in the parrot. The 

 "animals most susceptible to inoculation with the human type are the 

 guinea-pig, rhcesus, 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 shown 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. 



On glycerin agar and on serum, the growth of tubercle bacilli from 

 birds is more luxuriant, has a, moister appearance (Fig. 75, C), and, 

 moreover, takes place at a higher temperature, 43 - 5° C, than is the case 

 with mammalian tubercle bacilli. Experimental inoculation brings out 

 even more distinct differences. Tubercle bacilli derived from the human 

 subject or from the ox, for example, when injected into fowls, usually 

 fail to produce tuberculosis, whilst those of avian origin very readily do 

 so (on the other hand, the parrot is susceptible to inoculation with both 

 mammalian types). Fowls are also very susceptible to the disease when 

 fed with portions of the organs containing avian tubercle bacilli, but 

 they can consume enormous quantities of phthisical sputum without 

 becoming tubercular (Strauss, Wurtz, Nocard). The Royal Commission 

 found that rabbits and mice are the only mammals susceptible to 

 inoculation with avian tubercle bacilli, though others may succumb to 



