IN BOVINES 333 



dangerous channel of infection in tuberculosis.* At the same time 

 experience shows that the degree of infectivity of phthisis is not a very- 

 high one. It is a truly infective disease, but not an extremely 

 infectious disease. It may be rightly described as sub-infectious.^; 



Toxins of the Tubercle Bacillus. — Many investigators have isolated 

 products from pure cultures of the tubercle bacillus. These have 

 comprised chiefly albumoses, alkaloids, various extractives, and inorganic 

 salts. Koch isolated " tuberculin " from cultures of tubercle bacillus 

 upon glycerine broth by means of evaporation and precipitation with 

 alcohol. Buchner obtained by trituration and compression of fresh 

 tubercle bacilli a substance termed " tuberculo-plasmine." But of 

 the real nature of the toxins of the tubercle bacillus little is known. 



Bovine Tubereulosis 



Cattle come first amongst animals liable to tubercle. Horses may 

 be infected, but it is comparatively rare, and among small ruminants 

 the disease is rarer still. Dogs, cats, and kittens may be easily 

 infected. Amongst birds, fowls, pigeons, turkeys and pheasants 

 the disease assumes almost an epidemic character. Especially do 

 animals in confinement die of tubercle, as is illustrated in zoological 

 gardens. 



Bovine Tuberculosis. — Eespecting the lesions of bovine tuberculosis, 

 it will be sufficient to say that nothing is more variable than the 

 localisation or form of its attacks. The lungs and lymphatic glands 

 come first in order of frequency, next the serous membranes, then 

 the liver and intestine, and lastly the spleen, joints, and udder 

 (Nocard). The anatomical changes in bovine tubercle are mostly 

 found in the lungs and their membranes, the pleurae. It also affects 

 the abdomen and its chief organs, the peritoneum, and the lymphatic 

 glands. In both of these localities a characteristic condition is set 

 up by small grey nodules appearing on the pleura and peritoneum, 

 the nodules, increasing in size, giving an appearance of "grapes." 

 Hence the condition is called grape disease, or Ferlsuchf. The organs, 

 as we have said, are equally affected, and when we add the lymphatic 

 glands we have a fairly complete summary of the form of the disease 

 as it occurs in cattle. In about half of all cases the lungs and serous 

 membranes become simultaneously affected, in about one-third the 

 lungs alone; and in about one-fifth the serous membranes alone 

 (Friedberger and Frohner). As has been pointed out by Martin, 



* For a discussion on the channels of infection in tuberculosis, see Carnet, 

 Tuberculosis, 1904, pp. 96-282; Flugge, Zeitsohrift fur Hyg. u. Jufek., Band 

 xxxviii., 1901. 



t Koch, Etiology of Tuberculosis ; in Brit. Med. Jour., 1903, i. , p. 593 (Hillier), 

 will be found a useful summary of modern views on the question. 



