STRUCTURE AND ATTACHMENTS OF MUSCLES. 89 



threads, each separated from, and at the same time 

 loosely connected with, the others by a sheath of 

 cellular membrane, enveloping it, but which is so 

 thin as not to obscure the colour of the fibre, or 

 attract notice unless specially looked for. Each 

 muscle is in its turn separated from the neighbour- 

 ing muscles by thicker layers or sheaths of the same 

 membrane, in some of the cells of which fat is de- 

 posited, especially where the interval between the 

 muscles is considerable ; and hence the elegantly 

 rounded form of the limbs, which without this fat 

 would present the rigid, sharp, and prominent out- 

 line which we see occasionally in strong persons of 

 a spare habit of body. From the loose texture of 

 the connecting cellular membrane, the muscles 

 enjoy perfect freedom of motion during life, and 

 admit of being easily separated from each other after 

 death, either by the knife, or by simply tearing the 

 cellular tissue. 



Muscles, speaking generally, may be divided into 

 three parts, of which the middle fleshy portion, 

 called the belly, is the most conspicuous and im- 

 portant. The other two are the opposite ends, 

 commonly called the origin and insertion of the 

 muscle. The belly is the bulky and fleshy part, by 

 the contraction or shortening of the fibres of which 

 the two ends are brought nearer to each other, while 

 the belly itself swells out in a lateral direction. 

 When we attempt to lift a heavy weight in the hand, 

 or to overcome any resistance, the muscles which 

 bend the arm may be seen and felt to start out, rigid 

 and well defined in their whole extent, while their 

 extremities tend powerfully to approach each other, 

 and of course to carry along with them the bones 

 to which they are attached. In consequence of this 

 tendency, if the weight be unexpectedly knocked 

 out of the hand before we have time to obviate the 

 result, the muscles, having then no resistance to 

 overcome, will contract violently, and throw the 

 H2 



