ASPECTS OF ADSORPTION PHENOMENA 217 



shown by Macdonald 1 , but only in the position and neighbourhood of 

 an injured spot. They correspond to the distribution of potassium 

 ions, and are interpreted by Macdonald as precipitates of the dye 

 caused by potassium. He finds, in fact, that fairly strong solutions 

 of potassium salts are capable of throwing down the dye. Since 

 neutral-red is a basic dye these results seem at variance with the 

 action of neutral salts on adsorption of these dyes as described in- the 

 preceding pages. I thought it of interest therefore to see whether 

 neutral-red behaves differently to the basic dyes on which my 

 experiments were chiefly performed. I found it, however, to behave 

 quite in the same way. I did not, indeed, notice any tendency to 

 precipitation even by 2-6 per cent. K.CI. There are evidently, then, 

 some other factors at work in the case of the staining by neutral-red 

 of the granules produced by injury in the axis-cylinder of nerve-fibre. 



Since congo-red showed itself to be particularly sensitive, to 

 electrolytes it would seem a suitable reagent for the detection of 

 electrolytes, if split off from injured tissue. I have tested the 

 behaviour of nerve-fibres to this dye. It is easily seen, under the 

 microscope, that only the cut ends of the nerve are stained and not 

 the uninjured parts of the fibre. I could not detect any appearance of 

 granules, but did not look for them under a high power. It was to 

 be noted also that connective-tissue fibres took the stain, as I imagine 

 because they were non-living. 



The fixation of adsorbed dye by heat has already been pointed 

 out. This fact is of interest in connection with Altmann's method of 

 using acid-fuchsin. The fixation of dye by electrolytes has also been 

 mentioned. 



Recently Emil Mayer* has shown that the affinity of the Nissl bodies 

 of nerve -cells for basic dyes is abolished by previous treatment with 

 neutral salts. This is in complete concordance with the results I have 

 described. 



It occurred to me that, considering the opposite action of neutral 

 salts on electro-negative and electro-positive dyes it should be possible 



1. Pice. Roy. Soc., 76, page 3Z5, 1905. 



2. Hofmeister's Beitrage. 7, p. 560, 1906. 



