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CHAPTER III. 

 ON THE MUSCLES. 



MUSCLES are the moving organs of the animal frame ; they consti- 

 tute by their size and number the great bulk of the body, upon which 

 they bestow form and symmetry. In the limbs they are situated 

 around the bones, which they invest and defend, while they form to 

 some of the joints a principal protection. In the trunk they are 

 spread out to enclose cavities, and constitute a defensive wall capable 

 of yielding to internal pressure, and again returning to its original 

 position. 



Their colour presents the deep red which is characteristic of flesh, 

 and their form is variously modified, to execute the varied range of 

 movements which they are required to effect. 



Muscle is composed of a number of parallel fibres placed side by 

 side, and supported and held together by a delicate web of areolar 

 tissue ; so, that if it were possible to remove the muscular substance, 

 we should have remaining a beautiful reticular frame-work, possessing 

 the exact form and size of the muscle without its colour and solidity. 

 Towards the extremity of the organ the muscular fibre ceases, and the 

 areolar structure becomes aggregated and modified, so as to constitute 

 those glistening fibres and cords by which the muscle is tied to the 

 surface of bone, and which are called tendons. Almost every muscle 

 in the body is connected with bone, either by tendinous fibres, or by 

 an aggregation of those fibres constituting a tendon ; and the union is 

 so firm, that, under extreme violence, the bone itself rather breaks 

 than permits of the separation of the tendon from its attachment. In 

 the broad muscles the tendon is spread so as to form an expansion, 

 called aponeurosis (ufo, longe ; viv^ov* nervus a nerve widely spread 

 out). 



Muscles present various modifications in the arrangement of their 

 fibres in relation to their tendinous structure. Sometimes they are 

 completely longitudinal, and terminate at each extremity in tendon, 

 the entire muscle being fusiform in its shape ; in other situations 

 they are disposed like the rays of a fan, converging to a tendinous 

 point, as the temporal, pectoral, glutei, &c., and constitute a radiate 

 muscle. Again, they are penniform, converging like the plumes of a 

 pen to one side of a tendon, which runs the whole length of the 

 muscle as in the peronei ; or bipenniform, converging to both sides of 



* The ancients named all the white fibres of the body viugu; the term has 

 since been limited to the nerves. 



