EHRLIGW8 SIDE-CHAIN THEORY 



197 



normal economy of the cell, the receptors in question are diverted from their 

 normal function. Stimulated by this derangement of its normal mechanism, the 

 cell produces new receptors, of the same type as those thrown out of action ; and, 

 acting in accordance with a physiological habit which may frequently be observed 

 in living things, the process is carried to excess. The superfluous receptors are 

 shed by the cell into the surrounding fluids, and it is these shed receptors which 



Fig. 30.— Paul Ehrlich (1854-1915). 



constitute the specific antibodies. The essential feature of these antibodies is that 

 they unite with the corresponding antigens. Ehrlich therefore endowed each of 

 his receptors with a special chemical grouping, the haptophore group, which entered 

 into chemical union with a corresponding group of the antigen. If neutralization 

 alone resulted from the union, the requirements were met at this stage. If, how- 

 ever, the antigen became altered in some other recognizable way, as in agglutination 



