STRIATED MUSCULAR FIBRE. 



193 



Fig. 93. 



are connected with the peculiarly Animal powers of the being. The latter is 

 with difficulty called into action through the nervous system, but is much 

 more readily excited by stimuli applied to itself; and this is employed to per- 

 form various movements, which are more immediately concerned in the Vege- 

 tative or organic functions.* 



226. When we examine an ordinary Muscle (from one of the extremities, 

 for example) with the naked eye, we observe that it presents a fibrous ap- 

 pearance ; and that the fibres are arranged with great regularity, in the direc- 

 tion in which the muscle is to act. Upon further examination it is found, 

 that these fibres are arranged in fasciculi or bundles of larger or smaller size, 

 connected by means of areolar tissue ; and when the Microscope is applied to 

 the smallest fibre which can be seen with the naked eye, it' is seen itself to 

 consist of a fasciculus, composed of a number of cylindrical fibres lying in a 

 parallel direction, and closely bound to- 

 gether. These primitive fibres present 

 two sets of markings or striae ; one set 

 longitudinal, the other transverse or 

 annular. By more closely examining 

 these fibres, when separated from each 

 other, it is frequently seen that each may 

 be resolved into Jibrillx, by the splitting 

 of its contents in a longitudinal direction, 

 as shown in Fig. 93. These fibrillae have 

 a peculiar beaded appearance, which will 

 be presently noticed more particularly. 

 It not unfrequently happens, however, that 

 when a fibre is drawn apart, its contents 

 separate in the direction of the transverse striae ; forming a series of discs, as 

 shown in Figs. 94 and 95. This cleavage is just as natural as the former, 

 though less frequent; and it leads us to a view of the composition of Muscu- 

 lar Fibre, somewhat different from the one commonly adopted. To use the 



Fig. 94. 



Fasciculus of Fibres of Voluntary Muscle; 

 the fibres separated at one end, into brush- 

 like bundles of fibrillse. 



Portion of Human Muscular fibre, separating into discs, by cleavage in direction of transverse stria. 



words of Mr. Bowmanj it would be as proper to say, "that the fibre is a pile 

 of discs, as that it is a bundle ofjibrillse; but in fact it is neither the one nor 

 the other, but a mass in whose structure there is an intimation of the existence 

 of both, and a tendency to cleave in the two directions. If there were a gene- 

 ral disintegration along all the lines in both directions, there would result a 



By some, the two classes have been spoken of as those of Voluntary and Involuntary 

 muscles; but this distinction is not correct; since every muscle ordinarily termed voluntary, 

 may be called into action involuntarily. 



t See Bowman on the Minute Structure and Movements of Voluntary Muscle: in Phil. 

 Trans. 1840. 



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