MUSCLE. 139 



mere optieal deception, and that one can never be positive 

 with respect to it unless it be observed that the margin in 

 question does not accurately follow every bend of the fasci- 

 culus. It is, therefore, difficult to be convinced of this in 

 mammalia ; but in all those larva? of insects which present 

 the broad transverse stria? of the fasciculi, discovered by 

 Miiller, the membrane, when the continuity of the proper 

 muscular substance of a primitive fasciculus has been broken 

 at a certain point, may be distinctly observed passing over 

 uninterruptedly from the one portion to the other. PI. IV, 

 fig. 4, represents such a fasciculus ; the membrane encompasses 

 it so loosely (this larva had been preserved in spirits of wine) 

 that a portion of the muscular substance could even change 

 its position within the cavity. The membrane, where entirely 

 isolated from the other parts of the preparation, shows itself to 

 be quite structureless, and, indeed, the sharply-defined ex- 

 ternal contour renders it very improbable that it should be 

 composed of areolar tissue. I, therefore, consider it extremely 

 probable that it represents the cell-membrane of the secondary 

 muscle-cell. It thus not only serves to isolate the fasciculi, 

 but forms an essential constituent part of them. PI. IV, 

 fig. 5, exhibits this structureless membrane upon a muscular 

 fasciculus of the pike ; this preparation, however, was not 

 quite convincing, inasmuch as the inferior edge of the fasciculus 

 was covered by muscles lying above it. By means of this mem- 

 brane, the muscular fasciculus remains, throughout its entire 

 existence, a cell with a closed membrane and a cell cavitv, 

 the latter being filled with a firm substance, the peculiar 

 muscular substance. It, therefore, clearly follows from the 

 above that nervous fibres cannot pass between the primi- 

 tive fibres (fibrils) of muscle ; and that the latter cannot 

 separate from their fasciculi, so as to pursue a more extended 

 and independent course, as is common with fibres of areolar 

 tissue ; since, in either case, the cell-membrane must be 

 ruptured. 



The true muscular substance, which is thus, in the first 

 place, formed as a secondary deposition upon the inner surface 

 of the secondary muscle-cell, and continues to be so deposited 

 until the entire cavity is filled, is composed in its mature con- 

 dition, of very minute longitudinal fibres, the so-called primi- 



