72 NON-STRIATED MUSCULAR FIBRE. 



57. The other form of Muscular Fibre, which, from the 

 absence of transverse striation, is distinguished as smooth or 

 non-striated, is found not in large masses, but in thin layers, 

 forming part of the wall of various hollow organs, such as the 

 stomach and intestinal canal, the bladder, the principal gland- 

 ducts, and the larger blood-vessels. In all these situations it 

 is so exclusively concerned in the performance of the vege- 

 tative or nutritive functions, and it is so entirely withdrawn 

 from the influence of the will, that it has been frequently 

 designated as " the muscular fibre of organic life ;" the striated 

 fibre, of which the voluntary muscles are composed, being 

 distinguished as the "muscular fibre of animal life." But 

 these designations are not by any means consistent with the 

 facts of the case ; for in a large proportion of the Molluscous 

 classes, the muscles of animal life are composed of non- 

 striated fibre, whilst the heart of Man and of other Verte- 

 brata, though a muscle of organic life, is made up of striated 

 fibre. In fact, the employment of the one or of the other 

 kind of fibre would seem to be chiefly determined by the 

 kind of contraction which is required from it ( 59). The 

 non-striated fibres are arranged, like those of the other 

 muscles, in a parallel manner into bands or bundles; but 

 c these bundles, instead of being them- 

 selves grouped into larger ones having 

 a like parallel arrangement, are gene- 

 rally interwoven into a kind of network, 

 having no fixed points of attachment. 

 The form of the individual fibres is 

 much more variable than that of the 

 striated kind, being often very much 

 flattened out ; and hence their general 

 dimensions cannot well be estimated. 

 By macerating a portion of this kind 

 of tissue in dilute nitric acid, each fibre 

 fibre, showing, a a, the ma y ^Q re solve<! into bundles of long 



spindle-shaped cells, and, . ,, -, -, , -,. n i . - 



b 6, the elongated nuclei ; spindle-shaped bodies, which, contain- 

 So?et!Mv Ce ^'iS? n a S elongated staff-shaped nuclei 

 similar ceil treated with (fig. 21), may be regarded as cells, al- 

 though it is difficult to distinguish their 



walls from their contents. This form of muscular tissue is 

 commonly mingled with a large quantity of the ordinary fibrous 



