BOVINE TUBERCULOSIS. 551 



(5) Tubercle bacilli may pass from the mother to the foetus in case of 

 tuberculosis of the uterus or advanced generalized disease 



Tubercle bacilli may be taken up by cattle in several different ways: 



(i) Fully nine-tenths of all diseased animals examined have been 



infected by inhaling the tubercle bacilli, dried and suspended in the air. 



(2) Fully one-half of all diseased animals examined have been infected 

 by taking tubercle bacilli into the body with the food. This implies 

 that both food and air infection are recognizable in the same animal in 

 many cases. 



(3) Animals are infected, though rarely, during copulation. In such 

 cases the disease starts in the uterus and its lymph glands, or in the 

 sexual organs and corresponding lymph glands of the bull. 



(4) Perhaps from one to two per cent of all calves of advanced cases 

 are born infected. Among the 200 cases of tuberculosis, including all 

 ages, which have been examined by the writer, there are about two per 

 cent in which the diesase is best explained as having been directly 

 transmitted from the mother during or before birth. 



We may define the dangers of infection somewhat more definitely by 

 the statement that in any herd, even in those extensively infected, only 

 a small percentage of the diseased animals, namely, those which are in 

 an advanced stage, or such as have the disease localized from the very 

 beginning in the udder, or the uterus, or the lungs, are actively shed- 

 ding tubercle bacilli. It is these that are doing most, if not all, of the 

 damage by scattering broadcast the virus. 



Disease of the udder is particularly dangerous, because the milk at 

 first appears normal for some weeks, and therefore would be used with 

 impunity. Moreover, the tubercle bacilli in the diseased gland tissue 

 are usually numerous. 



The condition of the milk in different stages of the disease is a ques- 

 tion of great importance and demands careful consideration. The 

 stock owner, in the absence of proper dairy or other official inspection, 

 is under serious moral responsibilities to remove from his herd those 

 animals in which there is even a suspicion of udder tuberculosis. Any 

 udder which is found to increase slowly in size without any indication 

 '^ inflammatory processes, recognizable by the presence of heat, pain, 

 and redness, and which becomes very firm without showing at first any 

 alteration in the appearance of the milk, should be regarded as 

 infected, the cow promptly segregated, and the entire milk rejected 

 until a diagnosis can be made by a veterinarian. 



