ATTACHMENT OF MUSCLES 



129 



plasmic network, so that it is difficult to say where one 

 fiber leaves off and the next begins. 



Attachment of Muscles. — Nearly all muscles that 

 bring about bodily movements as distinguished from in- 

 ternal movements, as of the 

 stomach or intestines, make 

 their contractions effective 

 through pulling upon hard 

 parts (bones in higher ani- 

 mals, shell-structures in 

 lower). The effect is to 

 bring about the bending of 

 joints. Muscles are at- 

 tached either directly or 

 by means of tendons ; these 

 are tough and inelastic ex- 

 tensions of the connective 

 tissue which encloses the 

 muscle fibers and binds the 

 bundles together. Good ex- 

 amples of tendon action are 

 found in the hand (Fig. 

 32). The muscles which 

 move the hand are so bulky 

 that if they were located in 

 the hand itself it would be 

 too clumsy to be of service. 

 The arrangement which is 

 actually present is that the 

 muscles are out of the 

 way in the forearm, whence they connect with their 

 point of attachment by long tendons which can be seen 

 and felt readily in the back of the hand and at the 

 wrist. 



Joint Motions. — Skeletal muscles usually operate, as 

 was said above, by causing joints to bend. Joints are of 

 many kinds, the most familiar being the hinge joint such 



Fig. 32, — Human Forearm and 

 Hand; to show how muscles in 

 the forearm are attached by long 

 tendons to the wrist and fingers, 

 (a) group of muscles that bend the 

 wrist and fingers. 



