1908-9.] MICROCHEMISTRY OF STRIATED MUSCLE. 407 
In the majority of the preparations studied the reaction is confined 
to the dim band, which is marked by regularly occurring longitudinal 
lines of a beaded character (Figs. 7 and 8). The droplets are usually 
of uniform size and depth of colour, and in some instances they form 
a continuous and unbroken line throughout the length of the dim 
band (Fig. 8) while in others there is a tendency for the fat to be 
aggregated in the outer zones of the dim band, leaving a narrow 
space immediately in the centre of the band, which is absolutely 
free from any trace of the scarlet stain (Fig. 7). This massing of 
the fat towards the poles of the dim band may advance yet farther until 
the fat appears at the extreme edges of the dim band with occasional 
faintly colored droplets in the central part (Fig. 8). 
Frequently, however, the fat is wholly limited to the light band 
(Fig. 10). An approximation to this condition is shewn in Fig. 9, 
where the greater part of the fatty material lies in the outer thirds 
of the light band, but an occasional trace is also visible in the dim 
band. The striated character of the reaction is to be observed in 
the fat occurring in the light as well as in the dim band. The granules 
are visible in both cases and they always occur in longitudinal lines. 
Among those fibrils which had been subjected to treatment with Scarlet 
Red for five or more days occasionally was to be seen a result as 
represented in Fig. 11, where a granular longitudinal striation appeared 
in the light band, and an additional thin line of fainter colour, occurred in 
the dim band marking the position of Hensen’s line. The longitudinal 
granular character which is so distinctly marked in the dim band is 
maintained in the reaction along Hensen’s line. In the centre of 
the light band, extending horizontally across it, along Dobie’s line, is a 
narrow space devoid of any coloration. 
A clue to the explanation of these diverse pictures of the distribution 
of the fat is obtained from those fibres which have been fixed while 
a wave of contraction was passing over them (Fig. 12). In the lower 
contracted part of the fibril the fat lies wholly in the dim band, 
the centre of which is devoid of any reaction in contrast with the deeply 
stained red granules, regularly arranged in longitudinal lines in the 
zone on either side of this. Inthe upper part, where the fibre is uncon- 
tracted the dim bands shew only a diffuse reaction pale in colour with 
the fat in granules arranged along the borders adjacent to the light bands. 
The assumption, therefore, is that Fig. 7 represents the distribution of the 
fats in complete relaxation and Fig. 11 that of complete contraction, and 
the various intermediate stages are indicated in Figs. 8, 9, and Io. 
