112 FORM AND ACTION. 



The Structure of Muscles is fibrous. So many packets of 

 fleshy fibres, constituting in reality so many lesser muscles, dis- 

 posed in parallel lines, and united together into one mass of flesh, 

 form a distinct and separate muscle. But these packets are divisi- 

 ble into smaller packets, and these again are resolvable into fibres 

 of a still smaller description ; and of what the ultimate or primi- 

 tive fibres consist, or what their true nature may be, microscopical 

 observers are hardly yet agreed, some contending that they are 

 tubular, others that they are beaded filaments. Be which or 

 what they may, during life they possess the power of contracting 

 or shortening themselves; and through this vital property of con- 

 traction it is that all the motions and movements of the body are 

 effected. The order or stimulus for muscular contraction is given 

 by the brain, and conveyed to them through the medium of the 

 nerves ; and the action proves feeble or forcible, according to the 

 nature of the order or the amount of nervous energy emitted into 

 the muscle. What muscular contraction is, how the phenomenon 

 is effected, remains, after a host of minute and searching inqui- 

 ries, still problematic : we know little more about it than that it is 

 present with life and absent in death, and that, therefore, it is not 

 dependent on elasticity or any abstract physical force. 



The TENDONS or sinews with which most muscles are provided, 

 and which are different altogether in their appearance (being white) 

 and their texture from the muscles themselves, possess no power of 

 contraction, neither are they elastic : they can neither shorten nor 

 elongate. They are, in fact, simple cords connecting the mus- 

 cles with such parts as they are designed to put in motion, and, 

 being so much smaller than the muscles themselves, are on that 

 account capable of being intruded into the composition of parts, 

 without adding inconveniently to their bulk, or destroying their 

 symmetry. Through the intervention of tendon, for example, mus- 

 cles situated in the arm flex and extend the foot. Had there been 

 no tendon or sinew, the fleshy parts of the muscles must have 

 been continued to the foot, thereby rendering the leg an awkward- 

 shaped appendage, as large round, or nearly so, as the arm itself. 

 The " back sinews," as the flexor tendons are commonly called, are 

 stout firm cords attaching the flexor muscles — forming the poste- 

 rior part of the arm — to the pasterns and foot. The more promi- 



