BACTERIA AND DISEASE 283 



adult, but the dose is generally 10-20 centigrammes. In- 

 jections of tuberculin have no troublesome effect on the 

 quantity or quality of the milk of cows or on the progress 

 of gestation. 



Tuberculosis of Animals. Cattle come first amongst 

 animals liable to tubercle. Horses may be infected, but it 

 is comparatively rare, and among small ruminants the dis- 

 ease 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. Respecting 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 fre- 

 quency, next the serous membranes, then the liver and 

 intestines, 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 internal membrane lining, the abdomen and 

 its chief organs, the peritoneum, and the lymphatic glands. 

 In both these localities a characteristic condition is set up 

 by small grey nodules appearing, which increase in size, 

 giving an appearance of " grapes." Hence the condition 

 is called grape disease, or Perlsucht. 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. As has been clearly 

 pointed out by Martin, Woodhead, and others in their evi- 

 dence before the Royal Commission, the organs, glands, 

 and membranes are the sites for tubercle, not the muscles 

 (or " meat "). This latter is most liable to convey infection 

 when the butcher smears it with the knife which he has 

 used to remove tubercular organs. 



As regards the udder in its relation to milk infection, it 



