404 ’ ‘TRANSACTIONS OF THE CANADIAN INSTITUTE [VoL. VIII. 
fibril was not destroyed, he obtained similar results, but in no case was 
he able to discover that the fat bore any relation whatever to the cross 
striation. 
Of the mineral constituents of the muscle, the only element whose 
distribution has been studied microchemically is potassium. Macallum? 
has shewn that the salts of this metal possess a definite arrangement 
in the fibrils of uncontracted striated muscle, being limited to the 
dim band in the wing muscles of insects and the claw muscles of the 
crayfish but the potassium reaction was most marked in those zones of 
the dim band which are adjacent to the light bands. Inthe contracted 
fibril on the other hand he found that the most marked reaction for 
potassium was given by the central zone of the dim band. When, 
however, the penetration of the reagent (the hexa-nitrite of cobalt and 
sodium) is tardy there occurs a redistribution of the potassium salts 
in the fibres and in consequence the potassium demonstrated was some- 
times in the light bands alone and sometimes along the line of separation 
between two adjacent light and dim bands. 
II—THE LOCALIZATION OF THE FAT. 
To show the microchemical distribution of fat the reagent used 
was Scarlet Red, a stain belonging to the Tetrazo Compounds. This 
substance was introduced into microchemistry by Michaelis who 
studied its composition and properties, and by whom it was classed 
in the group of indifferent staining materials, which also includes Sudan 
III. It is insoluble in water, alkalies and acids, with the exception of 
concentrated sulphuric acid with which it gives a blue colour, soluble in 
alcohol and is readily dissolved in the fats. Its action is very much 
more extensive than osmic acid, which reacts only with unsaturated 
fatty compounds, such as oleic acid and olein, yet it stains nothing but _ 
the fats, whereas the osmic acid may be secondarily reduced by sub- 
stances other than the oleic compounds, and the resulting black precip- 
itate may represent more than the distribution of the fat.” Michaelis 
explains its action by the fact that it belongs to the indifferent sub- 
stances, i.e, those possessing no salt-forming group and whose acid or 
basic properties are so weak as to be practically negligible and, there- 
fore, the staining process is a physical rather than a chemical one, but 
that in order to be soluble in the fat the molecule of the staining 
compound must have a characteristic chemical composition. This 
latter statement seems to be borne out by the observation that palmitic 
and stearic acid crystals stain with some difficulty by Scarlet Red and 
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