INFECTIOUS DISEASES OF CATTLE. 437 



tubercle bacilli circulate in the blood and lymph and can they be 

 detected in the muscular tissue? 



(1) Disease of the bones is not unknown, although very rare. 

 According to Walley it appears chiefly in the spongy bones of the 

 head and backbone and in the long bones of the limbs. Occasionally 

 the ends of the bones, where they are covered by the synovial mem- 

 brane of the joints, are dotted with tubercles. The muscular sj^stem 

 itself is very rarely the seat of tuberculous deposits, although the 

 lymphatic glands lying near and among the muscles may be not 

 infrequently diseased. 



(2) Whether tubercle bacilli are found in muscle juice independent 

 of any tuberculous deposits is a question which must be approached 

 experimentally. There is on reeord a great variety of opinions on 

 this matter, some authorities considering all flesh from tuberculous 

 animals unfit for food, while others hold a contrary view. Experi- 

 ments have shown that in rare cases the flesh of tuberculous cattle 

 contains a small number of tubercle bacilli. In Germany the flesh 

 of animals in which the disease is just beginning, or in which it is 

 restricted to one or more related organs, is not rejected. AVhen, 

 however, the disease has affected the muscles, or bones, or lymphatic 

 glands situated on or between them, the flesh is condemned as unfit 

 and dangerous. Animals are also rejected in which it is evident, 

 from the general distribution of tubercles throughout the various 

 organs, that the bacilli have been distributed by the blood and may 

 have been carried into the muscular system (generalized tuberculosis). 



Concerning the infectious nature of milk secreted by tuberculous 

 cows, authorities have universally agreed that when the udder itself 

 is in the slightest degree involved the milk possesses infectious prop- 

 erties, and is therefore dangerous. Tubercle bacilli have been found 

 in large numbers in the milk and the udder under such circumstances. 

 Unlike other affections of the udder, tuberculosis of this organ does 

 not at once change the appearance and the quality of the milk 

 secreted. Bangs states that for at least a month after the disease has 

 appeared the milk is normal in appearance and may be consumed 

 and sold without arousing the suspicion of the owner. There is, 

 therefore, considerable danger involved in this disease, and the neces- 

 sity for the careful inspection of dairy cows seems more urgent than 

 ever before. 



Authorities are, however, not fully agi'eed as to whether the milk 

 from tuberculous cows in which the udder is apparently not invaded 

 by the disease should be considered dangerous or not. Some are 

 inclined to believe that the milk secreted by healthy udders is never 

 infectious, even when the lungs or other organs are affected; that, 

 in other words, the tubercle bacilli are rarely, if ever, separated from 

 the lesions which they produce, and that the udder itself must be 



