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a. 
THE MUSCULAR SYSTEM. 
MYOLOGY. 
By A. M. PATERSON. 
THE movements of the various parts and organs of the body are brought about by 
the agency of muscle-cells, characterised by a special histological structure and by 
the special function of contracting in length under the influence of a proper 
stimulus. The following section deals solely with the skeletal muscles, the 
structure, arrangement, and mechanical action of which are based upon a common 
plan. 
The cells of which the skeletal muscles are composed are long, narrow, and 
characterised by a peculiar striation, which is different from the striation of 
‘the muscle-cells of the heart; they also differ both in structure and function 
from the non-striated (and involuntary) muscle-cells which occur in viscera and 
vessels. 
A typical skeletal muscle consists of a fleshy mass enveloped in a membranous 
aponeurosis or fascia, and provided at its attached ends or borders with membranous 
or tendinous connexions to bone, cartilage, or fascia. 
Each muscle is made up of a number of fasciculi or bundles, arranged together 
in different ways in different muscles, so as to give rise to the particular form of 
the muscle in question. These fasciculi are connected together by a delicate 
connective tissue, the perimysium externum, continuous externally with the 
aponeurosis enclosing the muscle. 
Each muscular bundle or fasciculus is composed of a number of narrow, elon- 
gated muscle-cells or fibres, held together by a still more delicate connective tissue, 
the perimysium internum; this tissue is connected on the one hand with the sarco- 
lemma or cell-wall of the muscle-cell, and on the other hand with the coarser 
tissue of the perimysium externum enclosing the muscular bundles. 
By means of these connective tissue envelopes the muscle-cells, the essential 
agents of motor activity, are brought into firm and intimate relation with the 
osseous or other attachments of the muscle. Through the agency of sarcolemma, 
perimysium internum, perimysium externum, aponeurosis, and tendon, the muscle- 
cell when contracted can produce a precise and definite effect upon the weight to 
be moved. 
Each muscle is supplied by one or more nerves, which, after entering the 
substance of the muscle, separate into smaller and smaller branches, ultimately 
forming special terminal end organs in relation to each muscle-cell. 
While a muscle may thus be looked upon as an organ endowed with particular 
properties, and executing a definite movement in response to a stimulus, by the 
simultaneous contraction of its constituent cells, the various muscles may further 
be considered in groups, associated by mode of development, nerve-supply, and 
co-ordination of action. For example, we speak of the hamstring muscles of the 
thigh, the muscles of the back, and the prevertebral muscles, groups in which 
separate muscles are associated together by development, nerve-supply, and action. 
In their development the separate muscles arise from the subdivision of a larger 
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