UDDER-TUBERCULOSIS 89 



the lungs. In such cases the foci in the lungs and in the 

 udder are of the same age, the former more numerous than 

 the latter, however. 



As a rule, infection of the blood in the udder is caused 

 by tuberculosis in the lungs. Only exceptionally is udder 

 tuberculosis caused by tuberculosis in other organs, in which 

 the udder- and lung-infection occur at the same time. 



Infection through wounds is infrequent. I have only 

 seen one case of this kind. The wound becomes infected by 

 contamination with tuberculous products, such as coughed- 

 up tuberculous mucus. The contamination can be trans- 

 mitted by straw or the fingers of the attendants. 



Infection through the teat canal is less frequent than by 

 way of the blood stream, but more common than the wound 

 infection. The latter comparison is only natural, since the 

 teat canal is always present while udder wounds are some- 

 what infrequent. 



It is unreasonable to think that tubercle bacilli which 

 grow so very slowly can develop in the milk of the teat 

 canal, but one must consider that the infectious organism is 

 mechanically forced into the teat canal on a straw, for ex- 

 ample, which has been contaminated by coughed-up tuber- 

 culous mucus. 



If the udder is engorged with milk the distended teats 

 will be as firm as wood and the teat canals will be somewhat 

 widened as a result of this distention. Thus a hard straw 

 may be forced into the teat canal by movements of the 

 animal while lying down. 



Another possibility of infection is by the leucocytes pick- 

 ing up the infectious organisms and carrying them into the 

 udder. This, however, always necessitates contamination 

 of the point of the teat by tuberculous products either 

 directly or indirectly by straw or by the hand of the milker. 



Local Condition. — The lesions are in proportion to 

 the infectious material taken into the udder. The bacilli 



