OF THE MUSCULAR SYSTEM. 



211 



reticular connection, or termination in the interior of the mus- 

 cles, as to constitute contiguous prismatic bundles extending 



sideration the existence of fibrils very much minuter than the thoracic fibres, in the 

 muscles of Insects, and the gradual tran- 

 sition of the latter into undoubted bun- 

 dles, we do not hesitate to regard these 







Fig. 93 A. 



12 3 4 5 



5000 tos 



thoracic fibres as homologous, not with 

 primitive fibrils, but with primitive bun- 

 dles; and therefore to neglect any argu- 

 ment which may be drawn from their 

 existence, to that of primitive fibrils 

 during life in the higher animals. 



The answer to the question, whether 

 primitive fibrils exist during life or not, 

 in fact, depends very much upon the 

 meaning of the words. If it be meant, 

 that the muscular bundle is like a rope, 

 the fibrils being the separate strands, 

 united by "a homogeneous, tenacious 

 substance," — we should say that nothing 

 of the kind exists during life. If, on the 

 other hand, it be meant only that the 

 molecules of the muscle are so arranged 

 as to break up more readily and more 

 frequently in the longitudinal direction 

 than any other (just as a bar of wrought 

 iron would tear into longitudinal fibres 

 rather than in any other way, though it 

 could by no means be said that it was 

 composed of longitudinal fibres), why, 





R 



Fig. 93 A. 1, thoracic muscle of a Fly (musca domestica) unaltered, x GOO, from 

 an animal just killed : 2, similar fibre acted on by weak acetic acid, which distends 

 the matrix and separates the discs, rendering the whole at the same time excessively 

 pale : 3, a muscle of the leg, unaltered; the delicate fibrillation and the minute dark 

 sarcous elements, arranged side by side to form the " discs," are well seen ; a, nuclei 

 in the centre of the bundle : 4, the edge of a similar bundle, showing a very common 

 appearance — as if a row of minute sarcous elements were interposed between each 

 pair of larger ones, and thus giving rise to the appearance of the fine dark line be- 

 tween the discs: 5, the same treated with acetic acid, and showing this appearance 

 still more distinctly: 6, edge of a bundle treated with acetic acid, and exhibiting 

 none of the minute sarcous elements : 7, a bundle treated first with acetic acid and 

 subsequently with ammonia — sarcous elements very sharp and distinct : 8, 9, edges 

 of bundles of facial muscles of the Rat; in 8 with the minute sarcous elements, in 9 

 without them : 10, 11, 12, from the Frog; 10, a fibril in the ordinary state; 12, a 

 fibril greatly stretched ; 11, edge of a bundle, showing the large and distinct sarcous 

 elements, all of one size. 



i. 16 



