THE RECEPTOR APPARATUS OF THE RED BLOOD-CELLS. 393 



m 



FIG. 1. THE VARIOUS TYPES OF RECEPTORS ACCORDING TO EHRLICH. 



I. Receptors of the First Order. This type is pictured in a. The portion e 

 represents the haptophore group, whilst 6 represents a toxin molecule, 

 which possesses a haptophore group c and a toxophore group d. This 

 represents the union of toxin and antitoxin, or ferment and antifer- 

 ment, the union between antibody and the toxin or ferment being direct. 

 II. Receptors of the Second Order are pictured in c. Here e represents the 

 haptophore group, and d the zymophore group of the receptor, / being 

 the food molecule with which this receptor combines. Such receptors 

 are possessed by agglutinins and precipitins. It is to be noted that 

 the zymophore group is an integral part of the receptor. 



III. Receptors of the Third Order are pictured in III, e being the haptophore 

 group and g the complementophile group of the receptor. The com- 

 plement k possesses a haptophore group h and zymotoxic group 2; 

 whilst / represents the food molecule which has become linked to the 

 receptor. Such receptors are found in hapmolysins, bacteriolysins, and 

 other cytolysins, the union with these cellular elements being effected 

 by the amboceptor (a thrust-off receptor of this order). It is to be 

 noted that the digesting body, the complement, is distinct from the 

 receptor, a point in which these receptors therefore differ from those 

 of the preceding order. 



