228 Prof. A. B. Macallum. On the Nature of the [Mar. 3, 
reagent in sunlight. Alcohol of this strength* dissolves a considerable amount 
of sodium chloride and a smaller quantity of potassium chloride, and as the 
amount of each salt present in a section is small, the alcohol is capable of 
extracting it wholly, but leaving the proteids at the points where they came 
in contact with the alcohol. That the complete absence of a silver reaction 
in sections so treated is due to removal from them of the salts, was shown 
when the alcohol which had covered for several hours a large number of 
sections was completely evaporated, the residue giving a very distinct 
reaction for chlorides. 
When the preparations were covered for two hours with a mixturef of 
equal volumes of ether and acetone the greater part of chlorides were left in 
the sections, though not at the very points where they were during life, and such 
sections treated in sunlight with the silver reagent gave a marked colour 
reaction.t{ -When the sections were carefully dried and then placed in the 
nuxture for two hours their reaction was not perceptibly less marked than in 
fresh sections placed directly in the reagent. It was also found that: sections 
which were first dried, then kept in a quantity of the acetone-ether mixture 
for 2 hours, and finally treated for 10 hours more with 99 per cent. alcohol, 
gave on the addition of the silver solution no colour reaction. The residue 
left on evaporation of the alcohol consisted of minute crystals of chlorides, 
apparently of sodium and potassium. 
From all this it would appear that vegetable proteids, like those of the 
animal kingdom, do not give with nitrate of silver dissolved in a dilute solu- 
tion of nitric acid a colour reaction under the influence of light, and that the 
compounds in vegetable tissues which do react with the silver reagent are 
soluble in 99-per-cent. alcohol, but do not dissolve to any appreciable extent 
in the. acetone-ether mixture. These facts do not exclude the possibility of 
the participation of other compounds than chlorides in the reaction which 
vegetable tissues give, but they seem to indicate that if there are such com- 
pounds they must occur in excessively minute amounts, and their presence is. 
when the silver reaction is obtained, masked by that of the chlorides. 
* Sodium chloride is soluble in absolute alcohol to the extent of 65 parts in 100,000, 
and potassium chloride to the extent of 34 in 100,000 (De Bruyns, ‘ Zeit. fiir physik. 
Chem.,’ vol. 10, p. 783). 99 per cent. alcohol takes up a much larger quantity of each salt. 
+ Such a mixture if made from pure anhydrous acetone and ether, according to the 
author’s determinations, dissolves in 24 hours very little of the chlorides, 1,000,000 parts 
taking up only 2°4 parts of sodium chloride and 3°5 parts of potassium chloride. 
{ The acetone-ether mixture is a very rapid fixative for animal and vegetable tissues. 
Small pieces of kidney, liver, stomach, pancreas, thyroid and muscle when placed in it 
were rendered so firm in half an hour that very thin sections could be made from them 
with the section knife held in the free hand. The mixture is, on account of the rapidity 
of its action perhaps, not a serviceable histological reagent. 
