t68 manual of bacteriology. 



The reaction is very sensitive, the immune serum, as the 

 serum from the injected animal is called, causing clouding 

 in solutions containing very small traces of the homologous 

 serum. Rabbits are usually employed for the production of 

 immune sera for the precipitation reaction, and seem specially 

 adapted to the purpose. 



The reaction is of great value in determining the kind of 

 blood in any doubtful case, and is applied practically in forensic 

 medicine to determine the character of suspicious blood-stains. 



In the precipitin reaction, as this is called, there is group 

 precipitation, it is true. Thus, human and monkey's sera 

 react with the same precipitin and dog's and wolf's sera 

 respond to the same precipitin. Bacterial precipitins have 

 also been obtained by injecting animals with bacteria. In 

 this case filtrates obtained by filtering bacterial cultures 

 or suspensions through porcelain filters give a cloud, with 

 ultimate precipitation, when treated with a drop of homolo- 

 gous serum.* 



* Norris. The Bacterial Precipitins. Journal of Infectious Diseases. 

 Vol. I., p. 463. 1904. 



