Specificity of Agglutinins and Precipitins

The knowledge of serological reactions has opened a field of research dealing with the specific configurations existing in the chemical constituents of organisms. The results of agglutinin and lysin reactions and the use of the absorption method have disclosed an unexpected variety of structures as exemplified by the existence of differently reacting groups in a single kind of cells, of differences between individuals of the same species, of various types among bacilli of the same sort, and so on. The question whether the methods of absorption or partial saturation applied to precipitin reactions will disclose analogous facts is discussed in the present paper. Should this be the case, it might be possible to isolate antibodies which could serve to discriminate chemical groups contained in the protein molecules involved in precipitin reactions. For present purposes the nature of the precipitins reacting strongly on antigens of remote species will be left out of account because in their case special factors are possibly concerned. These reactions have recently been studied by Friedberger and his coworkers 1 and have been termed by them "heterogenetic precipitations."