LYSINS, AGGLUTININS, PRECIPITINS, ETC. 241 



assume the conditions conceived by Ehrlich, but that the phenomenon 

 of agglutination consists primarily of the union of the antibody with its 

 antigen in a colloidal suspension, and that the actual subsequent agglu- 

 tination is a purely secondary phenomenon which depends possibly 

 upon a change in the physical properties of the emulsion upon "its 

 colloidal stability." A similar condition he assumes for precipitins. 



Without being able in the limited space available to go into a de- 

 tailed discussion of the large volume of work which has appeared on 

 this subject, we may say that it is our opinion at present that the evi- 

 dence largely points in the direction indicated by Bordet, namely, that 

 the essential feature of all these reactions is the specific union of an 

 antigen with its antibody, that thereby the physical or chemical con- 

 dition of the antigen is so changed that it now becomes less stable and 

 is agglutinated or precipitated by such physical influences as, for in- 

 stance, the presence of an electrolyte. The work of Neisser and Fried- 

 mann 1 has shown that bacteria that have absorbed agglutinin are 

 agglutinated by concentrations of salt far less than is necessary to ag- 

 glutinate or precipitate the normal bacteria. 



Our own opinion, set forth in a number of experimental studies, 

 would go even further than this. We incline to the belief that all 

 antibodies, including the so-called amboceptors or sensitizers that take 

 part in the phenomena of lysis and bactericidal action are essentially 

 of one type; that the fundamental phenomenon is the union of the anti- 

 gen with the specific antibody or its "sensitization;" that by such sen- 

 sitization the antigen is now rendered on the one hand more easily 

 agglutinable or precipitable, on the other may be rendered more amen- 

 able to the action of the alexin or complement or to phagocytosis. 

 The agglutination and precipitation phenomena, moreover, are merely 

 evidences of the fact that these substances are in colloidal suspension 

 and are influenced by agencies which produce precipitations in such 

 suspension. It is interesting to note in this connection, also, that bac- 

 teria in neutral suspension carry negative charges which can be weak- 

 ened by sensitization with serum and weakened or reversed by the 

 addition of acid. These points tend to strengthen such a point of view. 



The degree of acidity necessary to reverse the normal negative 

 charge of bacteria corresponds roughly to that at which growth is inhib- 

 ited. This has led me to speculate whether or not vitality of bacteria 

 and the negative charge may be related. 



1 Neisser and Friedmann, Munch, med. Woch., 1904, li. 465-827. 



