PREVENTIVE MEDICINE 235 



This, however, is preventable, and owners of animals should see 

 that milkers are in the habit of cleaning the udders and washing 

 their hands before milking. 



Transmission by inoculation is very rare in animals, but cases 

 have been recorded in which man has been inoculated by handling 

 tubercular material. Tubercular mastitis may result from local 

 inoculation of an udder abrasion, and, according to Bang, the 

 bacilli may gain access to the udder via the teat canal and through 

 the medium of soiled litter. These methods of infection of the udder 

 are most probably very rare, infection usually occurring through 

 extension of a lesion within the abdominal cavity. Tuberculosis 

 of the udder in point of frequency depends upon whether it is the 

 practice in any particular herd to keep cows which are obviously 

 badly affected, since as a rule the udder becomes invaded at rather 

 a late stage of the disease. On an average somewhere about 1 to 

 2 per cent, of tuberculous cows have udder lesions (M'Fadyean). 



One very rare method of infection in cattle is per vaginam, 

 tubercle bacilli being transferred in a mechanical way by the bull 

 during coitus, and the bull may thus contract tuberculosis of the 

 penis. 



In advanced tuberculosis in pregnant cows, the uterus and 

 placenta occasionally become involved and infection is thus passed 

 from mother to fcetus. Tuberculosis of the uterus is, however, 

 very rare, and it is only in cases of uterine tuberculosis that this 

 method of infection occurs, and probably the number of calves 

 infected before birth does not exceed -2 to -4 per cent. This fact 

 has been elicited by the results of the tuberculin test in calves only 

 a few days old, and by the large numbers of post-mortem examin- 

 ations which have been made of calves not more than a few weeks 

 old. Knudzen* in Denmark in 1898 in over 13,000 slaughtered 

 calves found only -38 per cent, cases of congenital tuberculosis. 



PREVENTION AND ERADICATION. The prevention of the spread 

 of tuberculosis among cattle is of the very highest importance 

 owing to : 



(1) The loss of life which occurs annually among the infantile 



population. 



(2) The huge financial loss accruing to stock owners. 



(3) The fact that the disease among other domesticated animals 



owes its origin in most instances to bovine infection. 

 The inherent difficulties in eradication are (1) its very great 

 prevalence; (2) the slight economic loss which the disease inflicts 

 upon individual owners. At the outset it is to be pointed out that 

 *Journ. Comp. Path., 1899, Vol. XII., p. 189, quoted by Bang. 



