RECEPTORS 



53 



ing free receptors. This attenuated toxin is called by Ehrlich 

 toxoid. The receptors have been compared to a lightning rod, 

 which if placed within a building would, if struck, cause disaster, 

 while the same rod placed outside of the building, is a means of pro- 

 tection to the structure against lightning. This theory can be 

 applied to the production of other anti-bodies. If blood cell, 

 bacterial cell, or any animal fluid possessing a haptophore is capable 

 of combining with side-chains (receptors) of the cells of the immu- 



FIG. 17. a, receptor on cell; 6, toxin molecule; c, haptophorous portion of 

 the molecule; d, toxophorous portion; e, receptor. (Williams.) 



nized, just as a key fits a lock, then the cells are stimulated to pro- 

 duce excessive numbers of receptors, and these constitute the anti, 

 or immune body. It is possible to produce from rennet, egg-albu- 

 min, cow's milk, and from many other albuminous substances, 

 immune bodies by injecting these substances into animals. (Figs. 

 18, 19.) 



