290 



INFECTIOUS DISEASES 



with the toxic products of their growth. The culture medium is 

 then heated to a boiling temperature in order to destroy the 

 germs. It is then passed through a porcelain filter that removes 

 the dead germs. The remaining fluid is tuberculin. 



Tliere are iliree methods of applying the tuberculin test. Tlie 



flQ. 93. 



-A very large tubercular gland that had broken down in the central portion. 



subcutaneous test consists in injecting a certain quantity of tuber- 

 culin beneath the skin, and keeping a record of the body tem- 

 perature of the animal l^etween the eighth and eighteenth hours 

 following the injection. Tubercular animals show an elevation 

 in temperature that comes on about the eighth or twelfth hour of 

 the test. In the intradermal test, a small quantity of a special 

 tuberculin is injected into the deeper layer of the skin. The seat 

 of the injection in cattle is a fold of the skin on the under side 



