THE MUSCULAB SYSTEM. 



237 



Fig. 93. 



All 



except in macerated muscles, where such a thing readily occurs, 

 can only with difficulty be obtained in an isolated form, whilst 

 according to his view, such a disintegration, in cases where 

 these particles do not cohere firmly, either in a longitudinal 

 or transverse direction, would necessarily take place with equal 

 facility in either ; and in the second place, that in the thoracic 

 muscles of Insects, the individual fibrils may be very distinctly 

 and beautifully seen (fig. 93) in the muscles, when quite fresh. 

 When we consider the great similarity between 

 the muscles of insects and of the higher animals, 

 in every essential particular, this fact appears to 

 me to be of a striking nature. I am, there- 

 fore, from this and the other reasons assigned, 

 thoroughly convinced of the existence of fibrils 

 during life, and believe that, where they do 

 not so readily admit of being isolated, as in 

 man and many animals, they are connected 

 by a homogeneous, tenacious (albuminous), 

 interstitial substance, which is very evident 

 in a transverse section, and in fact so 

 firmly, that under certain circumstances, 

 transverse rupture of the fasciculi may take 

 place, that is to say, in the direction of 

 the thinner spaces of the fibrils ; as also 

 occurs in other fibres ; for instance, in the 

 elastic tissue, smooth muscles, and even in the corneous cells 

 (internal root-sheath and cortex of the hair). With all 

 this, it must not be supposed that fibrils exist in all mus- 

 cular fibres of animals, either themselves striped or cor- 

 responding to the striped fibres here described. The study 

 of development and of comparative anatomy much rather 

 teaches that the muscular fibre occurs in various conditions, and 

 particularly, that it frequently exhibits more homogeneous 

 contents, with or without transverse striation, and without 

 fibrils. This however, of course, affords no ground for the 

 assumption of such a condition in man and the mammalia also; 

 and although such muscular fibres, in certain animals, readily 

 break up into transverse segments (Leydig), still it is not thereby 



Fig. 93. Primitive fibres from a quite recent transversely-striated muscle of a Bug, 

 x 350 diam. 



