THE HISTOLOGY OF THE STRIPED MUSCLE FIBRE. 235 



amount of contraction of the matrix or sarcous substance, by exosmosis 

 for instance. The sarcolemma will follow this decrease in bulk but 

 will be prevented from doing so at those points where it is held out- 

 wards by the more rigid transverse networks. 



IV. The Living Fibre. 



The fibres from the leg of Dytiscus, or the bee, mounted without 

 the addition of any fluid, and examined whilst fresh or living, give 

 the appearances seen in figs. 19 and 20. Most of the fibres are seen 

 to present the appearance of alternate dim and bright bands, the dim 

 bands being the thicker. Each dim band is traversed by a series of 

 longitudinal lines of a highly refractile substance. Kunning across the 

 middle of the bright band transversely is seen a single row of dots. The 

 fine dark lines crossing the dim stripe are traceable at either end into 

 the dots of the bright stripe. In this case, just as in the acetic acid 

 preparations, there often appears to be a double row of dots in the 

 centre of the bright stripe. Fibres are seen side by side, one with a 

 single row, another with a double row of dots in this position. When 

 a double row is present, the corresponding dots of the two rows appear 

 to be always joined longitudinally by fine lines across the middle of 

 the bright stripe. This is mentioned by Haycraft 1 but not by Schafer. 



Sometimes again the appearance shown in fig. 20 is observed. A 

 series of short parallel longitudinal lines is seen in the position of the 

 transverse network. These lines appear dotted on careful examination. 

 This appearance is similar to that described in the acetic acid prepara- 

 tion (fig. 17), and may be explained in the same way as a perspective 

 view of the network crossed by longitudinal bright lines, caused by 

 refraction from the longitudinal rods. " Transposition" of the bands 

 may be seen on altering the focus, similar to that already described. 

 The line of dark clots, with its series of bright haloes forming the 

 bright disc, becomes now a line of bright dots bordered by two crenated 

 dark lines. The above observations on the living fibre were made by 

 means of the gas chamber. The chitinous integument of the leg of 

 the bee was slit longitudinally, the muscle scooped out, and quickly 

 teased on a cover-glass and inverted over the moist gas chamber. 

 This method may be used for studying the phenomena of contraction, 

 by blowing air charged with alcohol vapour into the chamber, and 

 thus causing the fibre to contract by chemical stimulus. 



1 'Quart. Journ. Micr. Sc.,' April, 1881, p. 23. 



