242 SPECIAL HISTOLOGY. 



the entire length of the muscle. These secondary muscular 

 fasciculi, as they are termed, are, each of them, enclosed by a 



there can be no question that such is the fact. The behaviour of a muscular fasci- 

 culus, under the alternate action of acetic acid and ammonia, is as instructive with 

 regard to this point, as that of bundles of connective tissue. 



The existence of varicosities of the fibrils must depend very much upon their state 

 of extension. Normally, they do not exist, unless, perhaps, the fibril has been split 

 off from the very edge of a bundle, where the sarcous elements often project strongly 

 (fig. 10G A, 4). When very much stretched again, since the sarcous elements are 

 more solid and resisting than the matrix, they will form knots, and the fibrils will 

 appear more or less varicose (fig. 93 A, 12). The great majority of instances in 

 which the fibrils appear varicose, however, depend on imperfect definition — and the 

 same may be said of supposed zigzag bendings ; while the spiral fancies, on the other 

 hand, are more probably connected with an imperfect judgment. 



Recently, Drs. Sharpey (' Quain's Elements') and Carpenter (' Manual of Phy- 

 siology') have advocated a view, the former, however, with some doubts (to which 

 Professor Kolliker does not refer), founded upon an examination of the preparations of 

 muscular fibrils, made by Mr. Lealand. They distinguish quadrilateral dark spaces in 

 the fibrillae, each of which is set, as it were, in a transparent frame of the same shape ; 

 these joined together constitute the fibril, the lines of junction of the frames, or "cells" 

 being indicated by a dark line. We have repeatedly seen the appearances which are 

 thus described; but so far as we have been able to discover, they invariably arise from 

 that peculiar interposition of rows of minute paler sarcous elements, between the 

 ordinary broad dark ones, to which we have referred above in describing the muscles 

 of Insects. In fig. 93 A, 13, we have represented the edge of a bundle of fibrils from 

 the heart of the Sheep, in which the structure described by Drs. Carpenter and 

 Sharpey appeared very obvious at first sight, — but on close examination, the dark lines 

 evidently proceeded from interposed rows of very minute sarcous elements. 8 repre- 

 sents the same appearance in the facial muscles of the Rat. 



Very often, the finer sarcous elements are completely wanting, as in the thoracic 

 muscles of Insects, in the muscles of the Frog (fig. 93 A, 10, 11, 12), and in many 

 of the bundles in Mammals, as in 9, from the facial muscles of the Rat ; and in these 

 cases there is, of course, no evidence at all of the existence of any such " cells." 



In conclusion, we may state the view which we are led to take of the structure of 

 striped muscle, in a few words. In a homogeneous, transparent matrix, definite par- 

 ticles are imbedded — the sarcous elements, — which are arranged side by side, in even 

 transverse rows. In some cases the sarcous elements are all of one size ; in others, 

 they are alternately larger and smaller. The reason of this difference does not at 

 present appear, but it is very possibly connected with the nutrition of the muscle. 

 The matrix usually tends to break up into longitudinal bands — the " fibrils,"— which 

 have the diameter either of a single sarcous element, or of some multiple thereof; it 

 likewise tends to break up in the transverse direction, giving way between the pairs 

 of rows (discs) of sarcous elements ; but these cleavage lines are no indication of the 

 existence of discs or fibrils, as such, in the unaltered muscle. The sarcolemina is 

 simply the outer portion of the matrix, and its demonstrability as a separate structure 

 depends upon the extent to which it is developed, and the amount of chemical change 

 which it may have undergone relatively to the inner portion. — Eds.] 



