50 



Scientific Proceedings (56). 



nor does it stimulate the thyroid causing increased protein 

 metabolism. 



29 (846) 



An experimental study of heredity in bovine tuberculosis. 



By Harlow Brooks, M.D. 



[From the Department of Medicine, University and Bellevue Hospital 



Medical College.] 



This study was conducted on what is probably the most valuable 

 herd of Holstein Fresian cattle in the world. It has now extended 

 over about ten years, hence several successive generations of stock 

 have been studied under precisely similar conditions. The experi- 

 ments have been supervised and verified by officers from the U. S. 

 Department of Agriculture and the data are matters of official 

 record in the register published by the Holstein Fresian Associa- 

 tion. I am permitted to summarize and publish the results of the 

 experiments by Mr. J. W. Dimick, the proprietor of Woodcrest 

 Farm, where the problem is under study. 



The number of animals comprised in the study is 425. The 

 animals were originally selected because of their desirability from 

 the standpoint of breeders and milkers or because of their "type" 

 and entirely independent of their being or not being tuberculous. 



The tuberculous animals greatly outnumbered the non-tuber- 

 culous and in most instances several generations of tuberculosis 

 on both sides is known to have existed. 300 tuberculous animals 

 were studied. The existence of tuberculosis was determined by 

 the administration of treble the official dose of tuberculin, repeated 

 in non-reacting animals three times at intervals of six months. 

 All animals reacting to either test were removed at once to the 

 tuberculous farm, the administration of which is entirely separate 

 from that of the non-reacting herd. Little or no possibility of the 

 transmission of infection from the tuberculous group to the healthy 

 one exists. 



With few exceptions tuberculous cows are bred to tuberculous 

 bulls, the selection in any case is made for purposes of "type" 

 and no account of the infection is taken in so far as breeding is 

 concerned. 



