INFECTION AND IMMUNITY. 575 



to dissolve alien erythrocytes, to digest such cellular 

 elements as epithelium and spermatozoa, to precipitate 

 milk, or agglutinate bacterial or blood-cells, as the 

 studies of Pfeiffer, Bordet, von Dungern, Moxter, Fish, 

 Belfonte and Carbon, Metchnikoff, Gruber, Durham, 

 Widal, and others, have demonstrated, then the process 

 becomes less simple, and the atomic grouping of the 

 receptive molecule is correspondingly more complex. 

 In some cases the receptor is provided with both a hap- 

 tophore and a ferment-like (zymophore) group ; the 

 function of the former being to combine with and hold 

 in close proximity to the latter the albumin molecule 

 that is to be destroyed or assimilated ; in this way 

 bringing and holding the albumin molecule directly 

 under the influence of the zymophore group. In other 

 cases the " receptor " functions symbolically, so to speak, 

 with a complementary something that circulates nor- 

 mally in the blood, the so-called " complement " of Ehr- 

 lich and Morgenroth. Under these circumstances the 

 " receptor " is conceived to be provided with two " hap- 

 tophore " groups, and becomes an " amboceptor," there- 

 fore, the one haptophore of which takes up and fixes 

 the invading bacteria, tissue-cell, or albumin molecule, 

 while the other pairs with the corresponding hap- 

 tophore of the complement, fixing the latter in close 

 proximity to the invading body, and thereby favoring 

 the immediate destructive activity of its " zymotoxic " 

 group. 



It is interesting to note in connection with this 

 hypothesis, that both " receptors " and " complements " 

 are present in normal susceptible, as well as in immune 

 animals, but that during immunization only the "recep- 



