438 COLLECTED STUDIES IX IMMUNITY 



of substances foreign to the bod}- synthetic processes play practically 

 no role whatever. If we take methylene blue as an example, we see 

 at once that we can easily find a large number of different fluids 

 which are able to shake it out. On the other hand, we know of a 

 large number of acids, like picric acid, phosphomolybdic acid, hyper- 

 sulphuric acid, which are able to precipitate the methylene blue in 

 insoluble form even out of very dilute solutions. This dyestuff , how- 

 ever, is practically useless for synthetic processes; all the efforts of 

 the chemists to introduce other groups into the completed molecules 

 (with one exception, nitro-methylene blue) have absolutely failed. 

 When we stop to consider that in such chemical procedures the 

 strongest possible agents can be used, sulphuric acid, high tempera- 

 tures, etc., we shall at once see that methylene blue cannot at all be 

 synthetically bound in the organism. The extensive distribution of 

 methylene blue, however, is very easily explained by the plentiful 

 opportunities offered for localization. 



Synthetic processes, such as occur in the absorption of foodstuffs, 

 in assimilation, and in the growth of living matter, are connected 

 with the existence of certain chemical groups, the "receptors." 

 These receptors are able to synthesize with fitting haptophore groups 

 of the foodstuffs or of the toxins, the two groups fitting specifically 

 to each other (like lock and key: E.Fischer). The eagerness with 

 which the living protoplasm lays hold of the foodstuff which it re- 

 quires is in marked contrast to the manner in which it resists taking 

 up substances foreign to itself. This was observed even in the begin- 

 ning of histology, for at that time it was regarded as an axiom that 

 living cells could not possibly be stained. Gerlach, for example, 

 had shown that an amoeba does not take up any coloring matter from 

 a solution of carmine, whereas it stains immediately when it is dead. 

 Since then, to be sure, largely through my efforts, we have come to 

 know a number of important vital stains (neutral red, methylene 

 blue, brilliant cresyl blue), but closer analysis of these phenomena 

 have shown that that which can be demonstrated in the living cell 

 by the various dyes is not the functionating protoplasm but its 

 lifeless (paraplastic) surrounding medium and the granules, etc., 

 present therein. In this point I agree entirely with Galeotti. 



