10 



becoming tuberculous. The reason why highly developed dairy herds 

 are often tuberculous is simply that the improvement of the herd is 

 generally based on the importation of breeding animals. This is the 

 cause of the infection. In this manner tuberculosis has often been 

 spread from large estates to the peasant farms, especially through 

 the sale of calves. 



As soon as tuberculin inoculation was undertaken on a large scale 

 the public was surprised at the very large number of reacting ani- 

 mals, even in herds of healthy appearance. I refer to the work as 

 done first by Koepp in Dorpat, then by Siedamgrotzky and Eber in 

 iSaxony, Nocard in France, Malm in Norway and others. 



The Danish investigations have yielded exactly similar results. 

 Where tuberculosis exists it often has an extent which no one had 

 suspected. The discovery produces atfirst a benumbing effect and is 

 always very painful to the owner of dairy stock. Because of this it 

 cannot be made too emphatic that there is a great difference between 

 what was formerly termed tuberculosis and what, as a result of the 

 tuberculin test, is now indicated by the same word. When a react- 

 ing animal is butchered, the butcher very often finds no trace of 

 tuberculosis and the veterinarian must search carefully to discover 

 the little knots on the lym|)h glands, frequently the only pathological 

 signs. 



These are, especially in the retro-pharyngeal, mesenteric, medias- 

 tinal and bronchial glands. The majority of reacting cows have 

 simply latent tuberculosis. In time this may develop further in 

 many cases. But my investigations have shown that such tubeicu- 

 losis can often remain without development for years, and exert no 

 influence on the gt'ueral health or the functions of the animal. We 

 cannot conclude from this observation that an animal which reacts 

 with tubeiculin is thereby condemned £o advancing disease, to wasting 

 away and final death. The reaction siniply indicates the possibility 

 of such a result. Whether or not it will prove a reality we do not 

 know. 



We must remember that the reaction gives very little light as to 

 how far tuberculosis has advanced in the body of the animal. The 

 intensity of the reaction is not in proportion to the amount of the 

 tuberculous deposits. It would be nearer correct to assert that these 

 two factors vary inversely to each other. A strong reaction is most 

 often noticed in slight cases, while cattle wliich have been affected a 

 long time frequently react only slightly or not at all. Hut this is by 



