Biological Therapy 



173 



treatment is of no value. Present efforts of control consist 

 of preventive measures such as disinfection and tuberculin 

 testing. The most approved procedure at the present time 

 consists of removing from the herd all affected and sus- 

 picious individuals and by conducting regular tuberculin 

 tests, insuring that no incipient cases of the disease remain. 

 In this manner it is possible to maintain a tuberculosis free 

 herd. 



DIAGNOSIS. While clinical diagnosis is possible in the 

 advanced stages of the disease it would be impossible to 

 control this disease if our sole dependence were placed 

 upon the recognition of clinical cases. Fortunately bio- 

 logical therapy offers a product fully capable of causing the 

 detection of animals affected with this disease. This product 

 known as tuberculin is available in several different forms. 

 Tuberculin is the end product of the tubercle bacilli and 

 is obtained by growing this organism on suitable culture 

 medium which after processing contains the desired active 

 principle, tuberculin. These products when used on tuber- 

 culous animals cause a characteristic reaction, whereas when 

 injected into individuals which are not affected with tubercu- 

 losis no reaction occurs. This reaction is thought to be 

 caused by the hypersusceptibility of affected individuals to- 

 ward the end product of the organisms causing the disease 

 with which they are affected. 



Tuberculin Tests 



For this purpose three tests are available : 



1. Subcutaneous. 



2. Intradermal. 



3. Ophthalmic. 



THE SUBCUTANEOUS TEST. This is the oldest and 

 most generally used method of detecting tuberculosis. While 

 the general principles of the test are understood by most 

 practitioners some information regarding details is fre- 

 quently desired. For that reason the following directions 

 for the subcutaneous tuberculin test taken from B. A. I. 

 publications are supplied. 



1. So far as practicable, the cattle should be stabled 

 under usual conditions and with usual surroundings. 



2. The cattle should be fed and watered in the custom- 

 ary manner, except that it should be done only immediately 



