262 DISEASES OF CATTLE, SHEEP, GOATS, ETC. 



CHECKS OR CONTROL ANIMALS. 



The following 11 untreated cattle, which were similar in age, 

 size, and condition to those given intravenous protective treatment ac- 

 cording to the methods of Pearson and Von Behring, were exposed 

 for the same length of time to the same tuberculous environment to 

 which the treated or protected animals were exposed. For the sake 

 of brevity only a sufficient account of these animals will be given 

 now to show that the environment contained the necessary amount 

 of virulent, infectious material to cause tuberculosis of most cattle 

 exposed in it. 



Heifer No. 471 contracted tuberculosis of the mediastinal and 

 mesenteric glands. 



Heifer No. 472 contracted tuberculosis of one post-pharyngeal 

 gland. 



Heifer No. 475 contracted tuberculosis of the mediastinal glands. 



Heifer No. 526 contracted tuberculosis of the mediastinal glands. 



Steer No. 530 contracted tuberculosis of the lung and medias- 

 tinal glands. 



Steer No. 531 remained healthy. 



Heifer No. 539 contracted tuberculosis of one post-pharyngeal 

 gland. 



Heifer No. 540 contracted generalized tuberculosis. 



Heifer No. 570 contracted tuberculosis of the mediastinal 

 glands. 



Bull No. 573 contracted tuberculosis of the lung and medias- 

 tinal glands. 



Cow No. 579 remained healthy. 



Of course it is to be understood that these cattle were carefully 

 tested with tuberculin and found to be free from tuberculosis be- 

 fore they were exposed as control animals in the experiment. It 

 is desired to avoid all detail not to some extent essential for a gen- 

 eral statement in the present report. 



In addition to the check or control cattle specially related to 

 the tests of the Pearson and Von Behring methods of bovo-vaccin- 

 ation, three other check animals were also introduced into the 

 same tuberculous environment, which was in all instances used as 

 the means to test the amount of immunity acquired by the treated 

 animals in these series of experiments. The three additional ani- 

 mals were Nos. 477, 484, and 549, and all three contracted tuber- 

 culosis as the result of the exposure. 



There was thus a total of 14 checks or controls, of which 12 

 became infected with tuberculosis, thus showing that the character 

 of the exposure to which the treated cattle were subjected was 

 quite severe. The time at which the various control animals were 

 introduced into the tuberculous environment and the length of 

 time they were permitted to remain in it were carefully planned 

 in connection with the exposure of the treated animals, so that any 

 failure among the latter to become infected could be properly- 

 valued through a comparison of the treated with the control ani- 

 mals. 



