CYTOLYSINS 93 



definite antibodies in the sera of the injected animals, and that such 

 antibodies are formed whenever foreign albumins either of animal 

 or vegetable origin are introduced through parenteral channels. 

 From their precipitating properties these substances have been 

 termed precipitins, while the corresponding antigen is termed 

 precipitinogen. 



Like the bacteriolysins, the precipitins have been shown to be 

 specific in their action, within certain limitations at least, and the 

 reaction has accordingly been used for the purpose of identifying 

 the origin of various albumins. In the form of the biological blood 

 test the principle is now generally utilized for the purpose of deter- 

 mining the origin of blood stains and upon the same basis it has 

 been possible to establish zoological relationship between different 

 animals (see Precipitin Test). 



Of special interest is the fact that a number of investigators are 

 now inclined to regard the agglutinating properties of the various 

 antisera merely as one form of expression of the more general 

 precipitating qualities of the same sera, so that according to this 

 conception the agglutinins as antibodies sui generis would have no 

 existence. It is supposed that agglutination among cells corresponds 

 exactly to agglutination among dissolved albuminous particles, which 

 latter process leads to what we are accustomed to speak of as pre- 

 cipitation. This view is supported especially by Kraus, v. Pirquet 

 and Wassermann. These observers could show that bacterial filtrates 

 are capable of binding agglutinin and that the filtrates in question 

 must hence have contained agglutinable substances. This is well 

 brought out if cultural filtrates are added to a corresponding 

 agglutinating serum in sufficiently large quantity. Under such con- 

 ditions the serum may lose its agglutinins entirely. If insufficient 

 amounts of filtrate are used, on the other hand, the agglutinating 

 titre remains unaltered, the difference in behavior being explained 

 by the assumption that much smaller quantities of precipitin are 

 required to cause agglutination than to bring about precipitation. 



Cytolysins. Further studies of the peculiar reaction of the animal 

 body to the parenteral introduction of foreign cells and their deriva- 

 tives then led to the discovery that antibodies of amboceptor type, 

 i. e., amboceptors of the nature of the bacteriolysins, are formed not 

 only following the injection of bacteria, but also upon immunization 

 with other cellular elements, using the term immunization in the 



