120 THE SIDE CHAIN THEORY 



in a series of experiments the subsequent agglutinative value 

 averaged only 1 to 106 as compared with 1 to 1093 in the control 

 animals, viz., in those which had been injected with non-agglutinated 

 organisms. 



On the basis of Ehrlich's theory the appearance of the so-called 

 natural antibodies in the serum can now also be accounted for in a 

 ready manner. Since the antibodies are not formed de novo, but 

 merely represent normal molecular complexes of the body cells, it 

 can hardly be surprising that once in a while, even in the course of 

 normal events, some of these side chains will be cast off, although no 

 bacteria or their toxins may have entered the body. That the anti- 

 bodies, moreover, which result on immunization with foreign cells 

 or cell products should be specific, is a necessary consequence, if we 

 accept the view that antibody production presupposes the existence 

 of a special affinity between the haptophoric groups of antigen and 

 antibody. The remarkable point in this connection indeed is not so 

 much the fact that the injection of a toxin should give rise to an 

 antitoxin, or of bacteria to corresponding lysins or cytotoxins, but 

 that so many varieties of antibodies should be possible for a given 

 animal. 



On the basis of Ehrlich's theory we are forced to conclude that 

 the cells of the body collectively must contain at least as many 

 different types of side chains preformed as the number of different 

 antibodies that can be theoretically obtained from a given animal, 

 and vice versa. This, however, does not seem altogether likely, if 

 we bear in mind the innumerable varieties of antibodies that can 

 actually be produced. I would only recall the possibility of obtain- 

 ing specific precipitins to the albumins of almost all the different 

 types of animals, then again the production of agglutinins not only 

 to different species of bacteria, but even to different strains of a 

 single species, etc. But it seems to me that even though we accept 

 Ehrlich's theory in its essential points that we need not suppose 

 the existence of such an enormous variety of receptors as occurring 

 preformed. It would seem perfectly plausible that though some 

 of the receptors, which we meet with as antibodies, may actually 

 exist preformed, that others are developed only when certain anti- 

 gens are brought in contact with certain cells, and in consequence of 

 a special "Bildungsreiz." Experiments in this direction have, so 

 far as my knowledge goes, not yet been made, but it should be 



