No. 7. DEPARTMENT OF AGRICULTURE. 175 



V. After a cow has been served by him they should be separated 

 at once and the cow sponged with a 3 per cent, solution of 

 creoline or carbolic acid before being returned to the main 

 stable. 



After 18 months or more of service it was noticed that these bulls 

 began to lose flesh and exhibit other symptoms indicating the advance- 

 ment of the disease. Their use as sires was discontinued, and later, 

 they were killed, and upon autopsy, showed generalized lesions of 

 tuberculosis. Even though, precautions Avere taken to prevent these 

 animals from endangering the herd, it is possible that they may have 

 been partially responsible for a percentage of the reactions obtained. 



It seems unfortunate that this herd should have been freed from 

 tuberculosis twice and as many times reinfected. However, I do not 

 believe that it is possible to keep a herd entirely free from tubercu- 

 losis in which new animals are being constantly purchased and en- 

 tered into the herd upon the tuberculin test at the time of purchase. 

 After a herd has been gotten free of tuberculosis the best manner to 

 keep from reinfecting the same is to endeavor to raise all animals 

 needed for future milkers, from the tuberculous free cows on the 

 farm. 



We shall now consider the second phrase of this problem, namely, 

 the value of the immunization of the young calves intended for future 

 members of the herd by the use of tuberculosis vaccine. 



The vaccine consists of tubercle bacilli of the human type which 

 have been found to be non- virulent for cattle, suspended in normal 

 saline solution. The particular culture known as Culture M, used 

 in the herd referred to was obtained from the sputum of a young 

 girl. The sputum upon miscroscopical examination contained vast 

 numbers of tubercle bacilli. Each microscopic field showed fifty to 

 one hundred bacilli. There did not appear to be any extensive pul- 

 monary tuberculous process upon clinical examination. The culture 

 was isolated in 1901 and its virulence was carefully tested upon 

 guinea pigs, rabbits, calves, sheep and horses. It was found if given 

 in larger quantities to bovine animals it was incapable of producing 

 lesions of tuberculosis. These injections were made subcutaneously, 

 intraperitoneally and intravenously. 



The suspension of the tubercle bacilli in the salt solution used for 

 the vaccination work was made so that 1 cc. of the suspension repre- 

 sented 1 milligram of dried tubercle bacilli. Fresh cultures were 

 used and no vaccine was prepared more than thirty-six hours prior 

 to injection. The vaccine was injected directly into the jugular 

 vein. 



During the years 11)04, 1905 and 1907 it was the policy to give the 

 calf the first vaccination when three to four weeks of age and sub- 

 sequent vaccinations at intervals of four to five weeks. Since 1907 

 the calves have been taken away from their dams soon after birth 

 and placed in a stable specially constructed for their care and which 

 can easily be disinfected at any time. Believing that there was no 

 danger of the calves contracting tuberculosis while kept in this 

 stable and fed upon pasteurized milk, the initial vaccination was not 

 given until the animal had attained the age of at least eight to ten 

 weeks. The interval between subsequent vaccinations was also 

 lengthened. 



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