CHAPTEE XXI. 



THE SIDE-CHAIN THEORY OF EHRLICH AND ITS 



RELATION TO THE THEORY OP 



PHAGOCYTOSIS. 



In 1885, before the discovery of toxins and anti- 

 toxins and before there was any knowledge as to piled to 

 the real nature of immunity, Ehrlich 1 published a 

 small volume on the "Oxygen Eequiremeiits of the 

 Body/' Herein the belief was expressed that the 

 assimilation of foods by cells is accomplished only 

 after chemical union has taken place between the 

 food substance and some constituent of cellular 

 protoplasm. It is not the understanding that as- 

 similation is at an end, however, when this union 

 has occurred, for certain molecules of complex- 

 chemical nature and of great size must be split up 

 into simpler substances before they can enter into 

 the composition of protoplasm. Therefore, the cell 

 constituent which combines with the nutritious 

 molecule serves only as a link to bring the food- 

 stuff into relation with the digestive, oxidizing or 

 fermentative activities of the cell. 



Ehrlich speaks of that portion of living proto- "L-eistungrs- 



T i -I .i n i , ... kern" and 



plasm which represents the cellular activities as side-Chains. 

 the "Leistungskern" of the cell, the center of cel- 

 lular activity, or the central group of the proto- 

 plasm, whereas those chemical groups which bind 

 the food substances are called the side-chains of the 

 "Leistungskern" 



The author of the theory has made his concep- 



1. Ueber das Sauerstoffbediirfnis des Organlsmus. 



