SIDE CHAIN THEORY OF EHRLICH. 



relation with the digestive activities of the cell. 

 Ehrlich calls that part of the living protoplasm 

 which represents cellular activity the central 

 group of the protoplasm. The chemical groups 

 which link or bind the food substances, he calls 

 the "side-chains" of the • protoplasm. The 

 theory of Ehrlich assumes that the "side- 

 chains" of a cell consist of clearly defined 

 groups of atoms which are capable of uniting 

 chemically with other definite groups of atoms 

 in food particles. The side chains themselves 

 he calls Receptors. To the uniting or combin- 

 ing groups of both the "side-chains" and 

 the pabulin, or molecular products of food Pabulin. 

 elements, he has given the name Haptophores. 

 As the different foods have different chemical 

 elements, Ehrlich believes they also have dif- 

 ferent binding (or combining) groups, (hap- 

 tophores) and that there also must exist many 

 kinds of receptors, each of which is able only 

 to combine with that form of food substance 

 which has a corresponding binding or combin- 

 ing group of atoms. Each special cell, as nerve 



or muscle, assimilates only that form of food ^oo^ . 



■^ Assimilation, 



suited to its own peculiar growth and develop- 

 ment. 



In a more recent announcement of Ehrlich 

 he summarizes as follows : 



"We must assume that all substances which enter into 

 the structure of protoplasm are fixed chemically by the 

 protoplasm itself. We have always distinguished be- 

 163 



