606 ANNUAL. REPORT OF THE Off. Doc, 



less expense than here. There certainly is a demand for that class 

 of meat fitted up in the highest possible shape. Even for the prize 

 stock that is produced for our large shows throughout the country 

 there is a demand; in the largest cities the supply is not equal to the 

 demand. There were a great many sheep that were shown at Chi- 

 cago and over in Canada, and everyone of those found their way 

 either to Boston or New York, to be used by those large clubs there. 

 If I were to tell you the price that some of those animals sold for 

 you would hardly believe me. I know one man who sold to a club- 

 house in Boston and a hotel in New York fifty yearling wethers at 

 an average price of twenty cents a pound dressed weight. If we 

 can keep any animal on our farm today that will net as much profit 

 as this I would like to know what it is; I would like to have some 

 of them. 



PREVENTION OF TUBERCULOSIS OF CATTLE BY VACCIN- 

 ATION. 



By LEONARD PEARSON, State Veterinarian, Harrisburg, Pa. 



For some years the State Livestock Sanitary Board has been 

 making experiments for the purpose of developing a method for 

 preventing tuberculosis of cattle by vaccination. 



This work was commenced nearly five years ago. It was at- 

 tempted at first on a very small scale, and afterward when it became 

 evident, about two years ago, that it was possible to increase the 

 resistance of an animal to tuberculosis to a very large degree by a 

 process of vaccination, the experiments were then taken up on a 

 large scale for the purpose of ascertaining whether it might be pos- 

 sible to develop a practical system for vaccinating cattle against this 

 prevalent disease. 



The process consists of injecting into the animal the living germs 

 of tuberculosis of a variety that is found to be non-virulent for cat- 

 tle. There are a great many varieties of the tubercle bacilli, vary- 

 ing in several respects, but chiefly in the degree of their virulence 

 for different species of animals. There are some varieties that are 

 absolutely non-virulent for cattle; that is, they do not have the prop- 

 erty of producing disease in cattle in any degree. The special strain 

 of germs that we are using for the vaccination of cattle is one 

 that has been very thoroughly tested; enormous quantities have been 

 injected into cattle with the view of ascertaining whether under any 

 circumstances it might possibly be harmful. It has been found it 

 is impossible by any process that has been used to infect an animal 

 with tuberculosis by the use of this special culture. Of course, 

 there are cultures that are deadly for cattle. The need for precise 

 information on this point is of the very highest importance. 



The process of inoculation consists of injecting a suspension of the 

 tubercle bacilli, the tubercle bacilli being mixed up in a solution 



