CHEMICAL CONSTITUTION AND PHARMACOLOGICAL ACTION 423 



posed of the same chemical substances, are subjected to different 

 conditions in the various tissues, conditions which may possess a 

 decisive influence. Foremost among these I regard variations in the 

 reaction and in the degree of oxygen saturation to which I have 

 already referred. As a result of my experiments in biological stain- 

 ing I assume that certain nerve endings, central and peripheral, are 

 characterized by a particular complex of such determining factors, 

 and that this "chemical milieu " represents the resultant of the normal 

 physiological functions Whether these views possess any heuristic 

 value for the further development of the science, I do not know. 

 For the present I shall content myself by remarking that the isolated 

 disease of nerve or muscle apparatus, so far as it affects certain par- 

 ticular groups (lead paralysis, arsenic paralysis), is readily explained 

 from this point of view. We shall have to assume the existence of 

 just as many different types of nutrition as we can demonstrate 

 different types of disease. 



This brings me to a further question which concerns this dis- 

 tributive therapy, and that is whether it is possible simply by chem- 

 ical means to change the type of distribution of a given substance. 

 This question can readily be answered ii the affirmative. If, for 

 example, a frog is injected with methylene blue, the nerve endings, 

 as is well known, will be stained in the living state. However, if 

 an easily soluble acid dyestuff, e.g. orange-green, is added to the 

 methylene blue solution so that a clear green solution results, it 

 will be found that the injection of such a mixture no longer produces 

 staining of the nerve endings. Hence we see that the conditions are 

 entirely analogous to those which we find in the staining of dry prepa- 

 rations. The basic dyes by themselves stain nuclei, whereas the 

 combination of basic dyes with acid dyes, which I introduced into 

 histological technique under the name of "triacid dyes," lack this 

 property to a greater or less degree. In both cases we are dealing 

 with a distribution of the methylene blue between the acid dye and 

 the tissue constituents. The tissues as well as the acid dyestuff have 

 an affinity for the methylene blue. If the affinity of the tissues is 

 greater, they will be stained blue, if that of the acid dye is the greater, 

 the staining will not occur. 1 



1 Naturally this phenomenon will occur conspicuously only in those cases 

 in which the tissue substances possess an affinity for the base only and not for 

 the acid dye If the latter condition obtains the mixture of both components 



