BACTERIAL POISONS. 



19} 



is regarded as analogous lo that produced by the injection of 

 bacteria, and consequently the serum of the animal injected 

 with albumin is spoken of as immune serum in the same way 

 as the serum from an animal injected with bacteria is so desig- 

 nated. The serum from the rabbit in the last example is 

 human serum immune-rabbit-serum. 



The term homologous is employed to denote the relation 

 between the immune serum and the albumin used in its pro- 

 duction. Thus, in the example just given, the rabbit's serum 

 and human serum would be called homologous the one with 

 the other. 



The reaction is very sensitive, the immune serum causing 

 clouding in solutions containing very small traces of the homol- 

 ogous 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 foren- 

 sic 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 ulti- 

 mate precipitation, when treated with a drop of homologous 

 serum.* 



*Noms. The Bacterial Precipitins. Journal oj Infectious Diseases. Vol. 

 I., p. 463. 1904 



