384 COLLECTED STUDIES IN IMMUNITY. 



internal metabolism. In accordance with the conception of Metch- 

 nikoff we must for the present believe that the leucocytes are pri- 

 marily concerned in their production. 



From these points of view the organism's immunity reaction loses 

 the mysterious character which it would have if the protective sub- 

 stances artificially produced represented a constituent originally for- 

 eign to the organism and to its physiological economy. 



But we have seen that immunity represents nothing more than 

 a phase of the general physiology of nutrition, a view in which I 

 agree entirely with that distinguished investigator Metchnikoff. 

 Phenomena entirely analogous to those of the formation of anti- 

 bodies are constantly occurring in the econonry of normal metabolism, 

 in all kinds of cells in the organism the absorption of foodstuffs, or 

 of products of intermediate metabolism, can lead to the formation or 

 the thrusting-off of receptors. Considering the large number of organs 

 and the manifold chemistry of their cells it need not be surprising 

 that the blood, which is representative of all the tissues, contains 

 an innumerable number of such thrust-off receptors. To these I 

 have given the collective name of "haptins." Only in recent years, 

 thanks to these very theoretical considerations, have we reached a 

 point where we can get some idea of this enormous multiplicity. 



In addition to the true ferments and those ferment-like sub- 

 stances, the complements, already mentioned, the blood normally 

 contains a number of substances which act specifically against cer- 

 tain substances present in solution. 



Chief among these I may mention the normal antitoxins, and as 

 examples of these the diphtheria antitoxin and antitetanolysin of 

 normal horse serum, the antistaphylotoxin of normal human serum, 

 and the anticrotin of pig serum. Next come the antiferments, 

 such as antirennin, antithrombase, anticynarase, and others. We 

 also normally find substances which prevent the action of specific 

 hsemolysins and bacteriolysins, being directed in one case against 

 the amboceptor, in another against the complement. For example 

 in goat blood I discovered an antiamboceptor which was directed 

 against a goat-blood hsemolysin obtained in accordance with Bordet's 

 procedure. In the blood of one animal species P. Miiller of Graz 

 found antibodies directed against certain complements of other 

 species of animals, and which may, therefore, be termed normal 

 anticomplements. 



Of still greater interest, however, are those haptins which are 



