CHEMICAL CONSTITUTION AND PHARMACOLOGICAL ACTION. 419 



extensive application in the histology of the nervous system. Then 

 there are the wonderful vital stains which the majority of granules 

 give with neutral red ; and the beautiful stains of these same 

 bodies which can be effected with brilliant cresyl blue (oxazin dye). 

 I cannot here enter into still other interesting and important vital 

 stains. 



Besides this each stain possesses its own peculiar characteristics. 

 Thus methylene blue, besides staining the nerve endings and a number 

 of the most diverse granules, stains intensely the cell protoplasm of 

 the islands of Langerhans of the pancreas, and, further, also muscle 

 cells of a certain particular function, striped as well as smooth. I 

 am practically convinced that in the vascular system certain muscle 

 fibres which can be stained with methylene blue cause a marked 

 narrowing and perhaps even a complete closure of the lumen after 

 the manner of a ligature. These muscle fibres never form a con- 

 tinuous lining of the vessel wall but only occur singly and separated 

 from one another by comparatively wide intervals. The uniform 

 calibration of the tube would then fall to the lot of the evenly dis- 

 tributed muscle lining which takes no stain. We should thus have 

 what is surely of great significance, namely, the fact that vessel 

 calibration and vessel closure are two functions which are absolutely 

 distinct anatomically and biologically. In a description so general 

 in character as this one I cannot enter into still other interesting 

 groups of dyes, e.g., those that stain nuclei vitally, etc. 



Exactly the same differences which we have observed in the case 

 of dyes manifest themselves if we introduce other kinds of sub- 

 stances into the body, it matters not whether they are well defined, 

 organic or inorganic combinations, or whether they constitute chem- 

 ically unknown and highly complex bacterial products. In general 

 we shall probably have to assume that substances which are chemically 

 well defined are to a great extent polytropic in character. In my 

 studies with several substances readily demonstrable by means of color 

 reactions and whose distribution can therefore readily be followed, 

 I have convinced myself that the aromatic bases as a rule have an 

 affinity for many different kinds of parenchyma. If in spite ot this 

 the clinical injury manifests itself in only one tissue, this in no way 

 contradicts the polytropic character of these substances. It merely 

 proves, what is really a matter of course, that among a number of 

 tissues there are some that are particularly susceptible to an equal 

 injury. To what extent other circumstances, such as saturation of 



