460 Veterinary Medicine. 



doctrine. Now, however, we recognize that congenital tubercu- 

 losis in man or beast is very exceptional, and that the morbid 

 process almost invariably takes its start from the germ implanted 

 after birth. In Saxony when the tuberculous cows were 16.5 

 percent, tuberculous calves were but_ .2 per cent., though the 

 latter had been fattened on the milk of the former. In Munich 

 but two calves were found tuberculous in 400,000 killed, and in 

 I^yons but five in a similar number. Up to the present the 

 number of calves recorded as tuberculous at birth does not exceed 

 seventy. 



That the young almost always contracted the disease, only after 

 birth, virtually disposes of the alleged heredity of the tuberculosis 

 but it by no means antagonizes the heredity of the racial vulner- 

 ability. As man, cattle, swine and Guinea pigs show a much greater 

 vulnerability than the carnivora in general, so certain families in 

 each of these genera show a more decided susceptibility to tubercu- 

 losis under similar conditions, than do certain other families. This 

 goes far to explain the appearance of tuberculosis, in certain lines 

 of blood, and its advance to the extinction of the family, while 

 under no better environment, other families can count on a prac- 

 tical immunity. In the Burden herd of Jerseys in 1877, I con- 

 demned eleven animals, verif3'ing my diagnosis by necropsies, and 

 found to my surprise that I had taken every representative, even 

 the grades, of a given family, and left all the pure bred members 

 of a second family untouched. Both families had mingled freely 

 in the pastures and yards, yet the second family furnished no 

 cases of tuberculosis then, nor for many years afterward. The 

 case is all the more striking that the non tuberculous family gave 

 the largest yield of milk and might have been expected to run 

 down rather than the other on account of this drain. 



Close Buildings. Lack of Ventilation. Air rendered impure 

 by being breathed again and again, predisposes strongly to tuber- 

 culosis, and has been even looked upon as the sole cause (Macor- 

 mac). Everywhere city dairy cows, kept in confined, close 

 buildings, suffer severely (6 to 20 per cent, and upward ; in Ber- 

 lin 75 per cent. (Ostertag), in Denmark 61 per cent. (Bang), 

 while in the same districts country cows are comparatively im- 

 mune (often I to 2 per cent.), and steers raised in the open air 

 still more so (0.02 per cent, for our Plains cattle). For the slighter 



