MECHANISM OF ANTIGEN-ANTIBODY REACTIONS 213 



the basis of the mass law is described. The derived expressions 

 are showTi to be in accord with the experimental findings and the 

 constants used in these expressions are shown to have definite 

 significance." In subsequent studies Heidelberger and Kendall 

 (1937) have shown that the same mathematical expressions hold 

 for rabbit as for horse precipitins in their reactions with pneumo- 

 coccus polysaccharides. An excellent summary of their work is 

 given by Chase and Landsteiner (1939). 



Reference to later work of Heidelberger and also of Hooker, 

 Eagle and others, liearing upon the controversies over the mecha- 

 nisms involved in cell sensitization and agglutination respectively, 

 is given in Chapter XI. 



Early Cataphoresis Experiment. — The second line of investiga- 

 tion whicli lias contributed to our present views involved experi- 

 ments to determine the action of bacteria suspended in a liquid 

 medium through Avhich a known electric current was passed. Such 

 studies on the cataphoresis of bacteria have been very fruitful. 

 The pioneer work in this field was probably inaugurated by Bech- 

 old (1904) and also by Neisser and Friedemann (1904). They 

 noted that bacteria that had adsorbed agglutinin clumped more 

 readily between the electrodes than bacteria that had not adsorbed 

 agglutinin. It suggested to them that perhaps adsorption of ag- 

 glutin was associated with a loss of electrical charge by the bac- 

 terial cells. In 1905, Pauli explained the agglutination of col- 

 loidal particles by electrolytes as due to the neutralization of 

 charges present on the dispersed particles. 



Powis ' Work and the Critical Potential. — The next important 

 contribution was made by Powis (1914) who studied membrane po- 

 tential changes in oil emulsions and found that coagulation oc- 

 curred when a critical P.D. of about 30 millivolts was reached. 



Similarity to Denatured Proteins. — In the same year Tullocli 

 suggested that sensitized bacteria, i.e., bacteria that had adsorbed 

 agglutinin, were comparable to denatured proteins. 



Buchanan's Suggestion (1919). — ^Buchanan reviewed the whole 

 subject of agglutination in 1919 and suggested that in a bacterial 

 suspension, the repelling forces resided in the similarity of charges 

 on the bacterial cells and these forces are opposed by those of sur- 

 face tension operating to cavLse agglutination. 



