268 MUSCLES 



that moves most is called the insertion of the muscle. 

 (See Fig. 115, A.) That attached to the end which moves 



Fig. 115— a, bones of the arm, showing origin and insertion of biceps (a) and 

 triceps (b) muscles ; B, a digastric muscle. 



least, is called the origin of the muscle. By following 

 with the fingers the curve of the biceps muscle, the tendon 

 that attaches it to the radius bone of the forearm and its 

 place of attachment to this bone can be readily felt. The 

 other end is covered with other masses of muscle, but dis- 

 section shows it to end in two tendons which are attached 

 to the shoulder blade. In bending the forearm, it is 

 evident that the radius moves most; hence the radius end 

 of the muscle is its insertion in this case, and the shoulder 

 blade its origin. 



It must be noted, however, that these terms insertion and 

 origin are merely relative terms. For example, in the oper- 

 ation of " chirming " oneself on a horizontal bar the 

 radius bone remains fixed and the shoulder blade is the 

 bone moved. In this case the radius end is spoken of as 

 the origin of the muscle, and the shoulder-blade end as the 

 insertion. Most muscles, however, are so arranged that 

 one end is always the insertion and the other the origin. 



Many bellied muscles have a single tendon at each end. 



