392 CHRONic INFECTIOUS DISEASES 



(d) Through the teat canals tubercle bacilli from contami- 

 nated bedding, manure, etc., may reach the udder, inducing a 

 primary tubercular mastitis. A general infection from this 

 source is seldom noted. x 



(e) While infection through skin wounds is not infrequent 

 in man, in animals it rarely occurs. In swine and cattle it 

 has been observed to follow the use of raw milk' applied to 

 fresh castration wounds. Accidental wounds of the prepuce 

 in bulls and udder in cows, in contact with contaminated 

 litter, bedding, etc., can form ports of entry for infection. 



(/) Congenital (intra-uterine infection) is rare. It may 

 occur if tuberculosis of the uterus is present and in advanced 

 generalized tuberculosis (uterus intact). 



Conceptional or germinal tuberculosis (infected sperm or 

 ova) has not been proved. 



Modes of Elimination. — In cases of "open" tuberculosis 

 the bacilli may be eliminated from the body through the fol- 

 lowing channels: (a) By coughing out or otherwise ejecting 

 infected bronchial exudate through the nose and mouth; 

 '(b) with the feces contaminated with swallowed bronchial 

 slime or from the discharge of tubercular ulcers in the mucous 

 membrane of the digestive tract; (c) 1 the milk will contain 

 tubercle bacilli if the udder is infected,, or When advanced, 

 generalized tuberculosis is present, and the udder seems 

 intact; (d) the urine contains tubercle bacilli when the renal 

 pelvis or parenchyma is tuberculous or in tuberculosis of the 

 . reproductive organs (vagina, uterus, prostate, epididymis), 

 the contaminated exudate or secretions afterward mixing with 

 the urine. 



Tuberculosis is essentially a. stable disease in that the 

 opportunity for infection and spread is greatest where ven- 

 tilation, light, and cleanliness are inadequately provided. 

 Further, in stables the animals are in closer contact with one 

 another than in the open. However, tuberculosis is observed 

 in cattle which are never housed and hogs are frequently 

 infected when out of doors following tuberculous cattle. As in 

 other contagio-infectious diseases, darkness, dirt, and foul air 



1 The milk of apparently healthy cows which react to the tuberculin test 

 only occasionally contains tubercle bacilli. 



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