264 DISEASES OF CATTLE, SHEEP, GOATS, ETC. 



with the check or control animals, among 14 of which only 2, or 

 14 2-7 per cent, escaped. 



If the only question to be considered in connection with bovo- 

 vaccination was the protection of cattle against tuberculosis, the 

 foregoing results would give us excellent reasons to be very cheer- 

 ful. Lately, however, studies made by various investigators on 

 the elimination of tubercle bacilli, after injection, from the bodies 

 of animals teach us to be very careful about adopting methods of 

 immunization for purely economic purposes that may be danger- 

 ous for those who afterwards use the products of the treated ani- 

 mals. 



The work of the Bureau of Animal Industry in the past has 

 also demonstrated that tubercle bacilli injected into the circulation 

 or under the skin of cattle may remain incorporated in their tis- 

 sues for long periods of time ; with only a gradual or very slow 

 loss of virulence. These are important factors that must not dis- 

 courage further work to build on the knowledge we have gained, 

 but which must be kept in mind and be permitted to have their 

 due influence on our subsequent investigations. 



Very careful autopsies of cattle treated by intravenous inocu- 

 lation of tubercle bacilli according to the methods of Von Behring 

 and Pearson show that the more or less attenuated tubercle bacilli 

 that engender immunity against tuberculosis rarely leave the treated 

 subjects wholly free from lesions that can be accounted for in any 

 other way than as due to the pathogenic activity within the ani- 

 mal's body of the injected bacilli. 



TEST OF THE HEYMANNS METHOD OF BOVO-VACCINATION. 



A protective treatment for cattle against tuberculosis, named 

 the Heymanns method after its inventor, has received considerable 

 attention during the last few years. The technique of this method 

 was demonstrated in America by Prof. Heymanns himself during 

 the meeting of the International Congress on Tuberculosis at Wash- 

 ington in 1908, and the efficiency of the method has been care- 

 fully tested by the Bureau of Animal Industry with cattle and 

 hogs. 



Heymanns's method, briefly, is the introduction of virulent 

 bovine tubercle bacilli, enveloped in a closed sack of vegetable 

 fiber, which in turn is inclosed in a gelatin capsule, under the 

 skin of the animal to be protected. The supposition is that the 

 vegetable sack will confine the tubercle bacilli at the seat of inocu- 

 lation and that the treated animal will be immunized by protective 

 fluids that form within the closed vegetable sack and pass outward 

 from it, into the animal's system generally, by an osmotic process. 

 The closed sack of vegetable material in combination with the 

 gelatin capsule is commonly known as the Heymanns capsule. 



In the fall of 1908, 12 cattle and 10 hogs were inoculated 

 with Heymanns's capsules. The animals were divided into three 

 groups, and one group of hogs and cattle were exposed immediately 

 after treatment to a tuberculous environment, a second about 2 

 months later, and a third about 2 months after the second. With 



