XXVI l'RESIDEXTI.\L ADDRESS. 



fat stock, the dairy fanner, and even the bullock driver, all of 

 whom are anxious to possess sound and healthy animals with 

 vigorous constitutions. Stock-breeders should bear in mind that 

 the predisposing cause can under no eircumstaces result in 

 tul)erculosis without action of the essential cause ; and the 

 tul)ercle bacillus is certain to produce its specific pathogenic effect 

 in tissues that are im2:)aired by hereditary or acquired causes. As 

 for Koch, whose authority in the matter is undeniable, he declares 

 that although he has conducted hundreds of most crucial experi- 

 ments, he has never seen any of his female guinea-pigs, when 

 tuberculous, transmit the disease to their offspring. According to 

 him, hereditary tuberculosis finds its most natural explanation ; 

 for what the mother does transmit to its offspring is not the 

 disease itself, but the predisposition or proneness to contract the 

 disease. In other words, the offspring is born tuberculizable 

 not tuberculous. 



These well-established facts tend to prove that heredity plays 

 a very small part, and contagion a great part, in the propagation 

 of bovine tuberculosis, and that if the young born of tuberculous 

 parents were protected from cohabitation, and the ingestion of 

 tubercular milk, the importance of heredity as a caxise of the 

 disease or even the predisposition to it would gradually dwindle 

 away into insignificance. In Denmark, Prof. Bang has shown 

 that by exercising a little care, and the free application of 

 tuberculin, how comparatively easy it is to protect cattle from 

 infection, and how a healthy herd may be bred from a severely 

 infected one. 



As evidence of this, Nocard says : "I had occasion to test 

 with tuberculin all the animals on a large and fine farm in the 

 north of France ; 5"> out of 105 were tuberculous — 46 out of 57 

 adults ; 9 out of 42 aged from four months to two years. Tw-nty 

 months later I repeated the test on 80 of the young animals 

 which had escaped infection, and on 14 more which had been 

 born since the first trial. Of this number 25 were bora of 

 tuberculous mothers. Not one of these animals gave the slightest 

 reaction — not one had become tuberculous ; and most of them 

 are now two, two and a-half, three, and more years old." 



