682 COLLECTED STUDIES IN IMMUNITY. 



on the principle of anchoring the antibody to the haptophore 

 group. 



Without going further into this subject, I wish merely to em- 

 phasize the fact that there are a number of foodstuffs, mostly probably 

 albuminous in character, which find specific receptors on the cells, 

 and that we are thus enabled by means of immunization to draw 

 these receptors into the blood. Here they present themselves in 

 various forms as agglutinins, precipitins, amboceptors, and opsonins, 

 and as antitoxins and antiferments. By causing them to accumulate 

 in the blood we can subject these substances to minute analysis, 

 a procedure entirely out of the question so long as they remained 

 part of the cell. The extent to which the analysis of these reactions 

 can be pursued is well illustrated by the study of the toxin-antitoxin 

 combination and by the recognition of the complex character of the 

 amboceptor action. 



This, of course, does not by itself solve the mystery of life. Com- 

 paring the latter to the complex structure of a mechanical apparatus, 

 we might say that we are at least able to take out some of the wheels 

 and study them minutely. This is certainly a great advance over 

 the former method to smash the entire apparatus and then hope 

 to learn something from the mass of fragments. 



I term all the receptors which are enabled and designed to assimi- 

 late foodstuffs for the cell "nutri -receptors." I consider that these 

 nutri-receptors constitute the source of the antibodies mentioned 

 above. From a pluralistic standpoint it is, of course, necessary to 

 assume that there are a large number of nutri-receptors of various 

 kinds. In view of the complexity of the organism, and of the 

 multiplicity and specificity of the cell functions, a standpoint other 

 than this appears out of the question. In immunizing we can dis- 

 tinguish three classes of nutri-receptors, namely: 



1. Those which do not pass into the blood in the form of anti- 

 bodies. We may assume that this is the case with nutri-receptors 

 serving the very simplest functions, as, for example, the absorption 

 of simple fats and sugars. 



2. Those which pass into the blood in the manner described 

 above, forming characteristic antibodies. The production of these 

 corresponds to a superregeneration. 



3. The third form contrasts with the preceding, in that instead 

 of a regeneration, there is a disappearance of receptors. Experi- 

 mental evidence of the occurrence of this form, to be sure, has thus 



