7 2 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tative or nutritive functions, and it is so entirely withdrawn 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/ 5 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 
these bundles, instead of being them¬ 
selves grouped into larger ones having 
a like parallel arrangement, are gene¬ 
rally interwoven into a kin d 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 
may be resolved into bundles of long 
spindle-shaped bodies, which, contain¬ 
ing elongated staff-shaped nuclei 
(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 
A B c 
Fig. 21. 
A, Portion of a band composed 
of non-striated muscular 
fibre, showing, a a , the 
spindle-shaped cells, and, 
b b, the elongated nuclei; 
B, a single cell isolated, and 
more highly magnified; C. a 
similar cell treated with 
acetic acid. 
