IMMUNITY 



127 



of preparation to render them assimilable. He conceived the 

 possibility then of a second order of receptors furnished like the 

 first with a haptophore portion for anchoring the food molecule, 

 and also with an additional portion which he called the zymophore 

 group, the special function of which was to prepare the food mole- 

 cule for absorption. 



FIG. 21. Diagram illustrating: A, Receptors of First Order; B, Receptors of 

 Second Order ; C, Receptors of Third Order. 



, ' Similarly, certain pathogenic substances which are more com- 

 plex than the toxins he assumed would combine with receptors 

 of this kind, the haptophore portion of the pathogenic molecule 

 combining with the haptophore portion of the receptor and acted 

 upon by its zymophore portion. 



Two such antibodies are known ; in one the zymophore por- 

 tion of the antibody causes clumping or agglutination of its antigen 

 and is consequently known as agglutinin. In typhoid fever the 



