RECEPTORS FIRST AND SECOND ORDER. 



17 



immune bodies is demonstrated in Figure 1, and represents the 

 type of receptor on which is based the action of bacterial toxin 

 and the formation of anti-toxin. 



Fio. 1. 



RECEPTORS OF THE SECOND ORDER. 



The receptors of the second order are distinguished from 

 those of the first order in that the receptors here have in addition 

 to the haptophore group, a zymophore group. This zymophore 

 group acts on the larger food particles, making them more readily 

 assimilable. In a similar manner it acts on the bacterial cell. 

 Receptors of this kind, possessing haptophore and zymophore 

 groups, are broken off from the cells and circulate in the blood as 

 agglutinins and precipitins after immunization by the injection 

 of certain bacteria. The haptophore group of the immune body 

 in an agglutinating or precipitating serum combines with the 

 bacterial cells. The zymophore group, however, does not com- 

 bine with anything but exerts its influences entirely through the 

 haptophore group. The zymophore group is destroyed by age, 

 acids, heating to 65 C., etc. Receptors and immune bodies of 

 the second order are represented in Figure 2. 



FIG. 2. 



