THEORIES OF IMMUNITY 



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channels, and the appropriation and eventual utilization of these 

 specific food materials by the cell. These nutritional substances 

 undoubtedly serve two purposes: Structural, to replace cellular 

 waste, and Fuel, to supply cellular energy. 



The nutritional requirements of the individual cell are varied as 

 their activities are varied, and Ehrlich conceives that each cell 

 possesses a number of chemical affinities or receptors, for convenience 

 of discussion designated as "side-chains" or "haptines," which are 



FIG. 6. Side-chains, second order (agglutinins and precipitins) . 1, side-chain attached 

 to cell; c, haptophore group; b, zymophore group (agglutinophore or precipitinophore 

 group) ; 2, side-chain to which is attached a bacterial cell ; a, haptophore group of 

 bacterial cell; 3, a' cast-off side-chain of the second order, agglutinin or precipitin; 4, 

 a side-chain attached to a bacterial cell (agglutination) ; 5, a bacterial cell ; a, hapto- 

 phore group; 6, an agglutinoid; the zymophore group is destroyed, leaving the hapto- 

 phore group intact. 



the means of attaching to the cell by chemical union, the essential 

 nutritive substances preparatory to their assimilation. When the 

 particular food attached to the cell by chemical affinity anchored 

 by the side-chain, to use Ehrlich's terminology has been assimilated, 

 more of the same kind of food is removed from the blood stream and 

 attached to the cell, in accordance with its normal physiological 

 requirement. The cell, acting through its side-chain, does not exhibit 



