PRECIPITINS 



Definition. All ol the foregoing experiments 

 have concerned themselves with the results obtained 

 by injection of cellular material of one animal into 

 another. In the further study of this subject, 

 experiments were made to discover what happens 

 when dissolved albuminous bodies of one species are 

 injected into animals of another species. This line 

 of investigation was first pursued by Tchistowitsch, 1 

 who injected rabbits with the serum of horses and 

 of eels. On withdrawing serum from such rabbits 

 and mixing it with horse or eel serum, the mix- 

 ture became cloudy, owing to the precipitation of 

 part of the albumin of the horse or eel serum by 

 that of the rabbit. Normal rabbit serum does not 

 possess this property. Bordet was able to demon- 

 strate that the same thing takes place if rabbits are 

 treated with chicken blood. On mixing such a 

 serum with chicken serum, a precipitate formed. 

 The substances which develop in the serum by 

 treating an anima 1 with albuminous bodies of 

 another animal, and which precipitate these a'bumins 

 when the sera of the two animals are mixed, are 



1 Tchistowitsch, Annal. Pasteur. Vol. xiii, 1899. 

 107 



