460 THE TUBERCLE BACILLUS GROUP 



bacilli may lead to false conclusions unless this possibility be borne in 

 mind. The bacillus of infectious abortion induces lesions in guinea- 

 pigs closely simulating tuberculosis. 1 This organism is rather widely 

 distributed in unheated milk. 2 



Method. Ten to 20 c.c. of milk are centrifuged for half an hour 

 and from 5 to 10 c.c. of the sediment and lower portion of the sample 

 are injected subcutaneously into guinea-pigs. The cream layer is 

 also injected subcutaneously into a second pig. After three to six 

 weeks, if the animal shows signs of emaciation, 0.5 cm. of undiluted 

 bovine tuberculin is injected. This injection usually results fatally. 

 In any event the animal is killed and the bovine tubercle bacilli are 

 identified in the usual manner. 



Immunity. Cattle and swine exhibit little or no natural immunity 

 to infection with the bovine tubercle bacillus. The most satisfactory 

 prophylaxis consists in isolating infected animals from the herd, 

 disinfection of the stables and testing all apparently sound animals 

 with tuberculin. 



Tuberculin Test. The preparation of bovine tuberculin is precisely 

 similar to that of human tuberculin, except that the bovine organism 

 is used. The test is carried out in the following manner: 



The temperature of the animal is taken at frequent intervals for 

 twenty-four hours, then tuberculin is injected subcutaneously, prefer- 

 ably over the fore-shoulder, about 10.00 P.M. Temperatures are taken 

 from 6.00 A.M. of the following morning at two-hour intervals until 

 10 P.M. An elevation of temperature of from one to three degrees 

 occurs within a few hours in positive cases and a hot swollen area of 

 induration appears around the site of inoculation. Both the febrile 

 reaction and the indurated area slowly become normal. The Inter- 

 national Commission on the Control of Bovine Tuberculosis 3 states: 



"1. That tuberculin, properly used, is an accurate and reliable 

 diagnostic agent for the detection of active tuberculosis. 



2. That tuberculin may not produce a reaction under the following 

 conditions : 



(a) When the disease is in the period of incubation. 



(b) When the progress of the disease is arrested. 



(c) When the disease is extensively generalized. 



' l Theobald Smith, Bureau of Animal Industry, 1894, Bull. 7, 80 Smith and Fabyan, 

 Centralbl. f. Bakt., Orig., 1912, Ixi, 549. 



2 Melvin, Vet. Jour., 1912, Ixviii, 528. Fabyan, Jour. Med. Research, 1913, xxviii, 85. 



3 Forty-seventh Annual Report of the American Veterinary Medical Association, 

 September, 1910. 



