Bovine Tuberculosis. 



Ill 



especially when they are fed tuberculous milk. The increase of tuber- 

 culosis in hogs is shown by the fact that in 1900, of 23,336,884 hogs 

 that were inspected by the Federal Government, 5,440 were affected 

 sufficiently to cause a condemnation of some one or more parts of the 

 carcass ; in 1905, of 25,357,425 hogs inspected post-mortem 46,919 car- 

 casses and 142,105 parts of carcasses were condemned for tuberculosis. 

 It should be remembered that the greater the percentage of tuber- 

 culous cows in the herd, and the further advanced the disease in the 

 cattle, the greater the danger of infection from the use of the milk. In 

 cases where the disease is restricted to small nodules in the lymphatic 

 glands, or perhaps in the lungs, the danger of tubercle bacilli being in 

 the milk is very slight, but when the udder is tuberculous they are con- 



FiG. 130. — Liver of a cozv shoi^'ing tiuo small tuberculous deposits. 

 They zvere the only lesions found. The cow gave a typical 

 tuberculin reaction. Natural size. 



stantly present in the milk and often in very large numbers. When 

 calves or pigs are fed with milk of this kind they are almost sure to be 

 infected. The same result may follow when it is fed to children or adults. 



Practically the only way tuberculosis gets into a herd of healthy cattle 

 is by the introduction of a tuberculous animal or animals. It has often 

 happened that farmers who have perfectly healthy animals buy a nice 

 looking cow that is tuberculous, although the disease was not at all in 

 evidence, and sooner or later this animal infects a very large number 

 of individuals in the herd into which it is brought. The buying of in- 

 fected animals and the feeding of calzrs with infected milk are largely 

 responsible for the spread of tuberculosis in cattle. 



The history of tuberculosis in cattle shows that when it is once intro- 

 duced into a previously uninfected district its tendency is to spread from 

 farm to farm with a rapidity which depends upon the activity of the cattle 



