436 COLLECTED STUDIES IN IMMUNITY 



This substance has the property of staining the granules of cells 

 most intensely, and the same holds true of a number of derivatives, 

 e.g. violet dimethyl neutral red, in which the two hydrogens of the 

 second amido group are replaced by two methyl groups; further, 

 also, the golden-red diamidophenazin: 



NH 2 N N(CH 3 ) 2 



In contrast to this, however, the combination in which one of the 

 central amin radicals contains an ethyl group which gives to the 

 group the character of an ammonium base, is absolutely unable to 

 effect the staining. All phenazin derivatives which stain granules can 

 be completely shaken out of weak alkaline solutions by means of 

 ether, whereas not even a trace of the ammonium base belonging 

 to the safranin series is thus taken up by the ether 



A very intimate connection, however, exists between solubility in 

 the test-tube and ability to be absorbed in the organism, a connection 

 which I observed as long as fifteen years ago. Hence we must assume 

 that certain fat-like substances of the nervous system as well as the 

 fat of fat cells possess a high solvent power by means of which these 

 substances are anchored or stored up in the tissue in question, just 

 as the alkaloids are taken up by the ether in the Stas-Otto pro- 

 cedure. 1 



If we bear in mind not only the extraordinary multiplicity of 

 Substances foreign to the body, but also the varying chemistry of 

 the tissues which make up the organism, we shall not expect that 

 a single principle can be rigidly applied to the phenomenon of 



1 This behavior has been studied especially by Overton. He terms the 

 substances of the brain which serve as extracting agents "hpoids." Chief 

 among these are cholesterin and lecithin Among the alkaloids Overton di s . 

 tinguishes feebly basic and more strongly basic substances. The former can be 

 shaken out for example, the indifferent narcotics; whereas the more strongly 

 basic unite with constituents of the cell to form salt-like combinations which 

 are very easily dissociated. According to Overtoil's conception therefore 

 Knecht's explanation would apply at one time and Witt's at another 



