406 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vou. VIII. 
the centre of the dim band and another on either side of this at- its 
upper and lower borders. In some case Hensen’s line appears as an 
exceedingly fine faintly colored thread (Fig. 3) and as the particles 
which compose it are often so fine as to be only discernible in the 
ultramicroscope, some conception may be had of their minute size. 
In many cases, however, the line appears equal in width to those on 
either side of it (Figs. 4 and 5). 
That this substance is undoubtedly fat is shewn by the fact that 
the fat solvents readily remove it from the fibres and if these are 
employed previously to the staining of the tissue with the Scarlet 
Red either no indication of the reaction appears, or one of very 
much lessened intensity depending on the time the solvent has been 
in contact with, and how readily it has penetrated the muscle fibres. 
For the purpose of demonstrating this, muscle previously fixed in 
formol was treated first with 70 per cent. alcohol for four hours then with 
absolute alcohol for twelve to twenty-four hours and finally with ether 
for from twenty-four hours to one week. The preparations were 
afterwards repeatedly washed with alcohol until every trace of ether was 
removed from them. Subsequent treatment with Scarlet Red fails to 
reveal any trace of a colored striation if the tissue has been suffi- 
ciently teased to allow a complete penetration of the ether. 
Where the tissue has not been thoroughly separated, although the 
muscle has remained in the ether for several days, the fat is not com- 
pletely dissolved out and the fibrils give on treatment with Scarlet Red 
a reaction characteristic in its distribution but of a much fainter colour. 
The final extraction of the fat occurring normally in the muscular tissue, 
is as Bogdanow® has shewn very difficult to obtain. He found that 
even after repeated extractions in a Sohxlet apparatus with ether - 
he could obtain a reaction with osmic acid in the muscle fibre. 
When the myoplasm surrounding the fibril has not been removed 
by the teasing, it stains a deep homogeneous reddish orange (Fig. 2) 
which apparently indicates a diffuse distribution of the fat in that 
structure. 
The distribution of the fat is not constant in any one part of 
the fibre alone. Most frequently it appears in the dim band, but it 
may occur only in the light band, and, occasionally, simultaneously 
in both. This variation seems to be intimately connected with the 
activity of the muscle, ie., whether the muscle is in the resting or 
contracting stage. 
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