MUSCLE-TISSUE. 



271 



The contraction of a muscle to the naked eye consists in the 

 shortening and the broadening of its belly. Accordingly, we see 

 under the microscope, in a contracted muscle-fiber, all the rows 

 of sarcous elements approaching each other, and every sarcous 

 element becoming broader. This is done at the expense of the 

 connecting filaments, which become shortened. The liquid be- 

 tween the rows spreads by 

 pressure in the transverse 

 direction. By contraction, 

 nothing is lost from and 

 nothing added to the mus- 

 cle-fiber. In extension the 

 muscle-fiber is elongated, 

 and accordingly the sar- 

 cous elements gain in 

 length and their rows sepa- 

 rate. Kanvier drew atten- 

 tion to the presence of two 

 lands of muscles even in 

 mammals, especially in 

 rabbits the pale trans- 

 parent and the red opaque 

 varieties. He claims that 

 the pale muscles contract 

 more rapidly, upon appli- 

 cation of the galvanic cur- 

 rent, than the red ones; 

 that the pale muscles have 

 a more marked transverse 

 and the red a more marked longitudinal striation, and also that 

 the nuclei of the pale muscles are less numerous than those of 

 the red. 



In transverse sections of muscle-fibers (see Fig. 112) we often 

 notice a central, pale, irregularly granular nucleus, or sometimes 

 two such nuclei. Instead of, or in addition to, granular nuclei, we 

 also see small, irregular, solid lumps of bioplasson in the midst 

 of sarcous elements, which formations correspond to the oblong 

 nuclei and to the rows of coarse granules in a longitudinal sec- 

 tion. From the central nucleus radiating offshoots emanate, 

 which interconnect the coarse granules, and group the sarcous 

 elements in circular or radiating formations, which are sometimes 

 very gracefully arranged. These are the celebrated muscle-nuclei 



FIG. 115. STRIPED MUSCLE OF THE CRAW- 

 FISH (ASTACUS FLUVIATILIS). STAINED 



WITH CHLORIDE OF GOLD. 



Si, row of large sarcous elements, splitting into 

 rows of smaller ones, S* ; between the rows of large 

 sarcous elements rows of small ones ; all rows inter- 

 connected ; N, nuclei on the surface of the fiber. 

 Magnified 1200 diameters. 



