80 



THE HUMAN BODY 



the origin the moved point; as for instance in going up a rope 

 "hand over hand." In that case the radial end of the muscle is 

 fixed and the shoulder is moved through space by its contraction. 

 Different Forms of Muscles. Many muscles of the Body have 

 the simple typical form of a belly tapering to a single tendon at 

 each end as A, Fig. 44; but others divide at one end and are called 

 two-headed or biceps muscles ; while some are even three-headed or 

 triceps muscles. On the other hand, some muscles have no tendon 

 at all at one end, the belly running quite up to the point of attach- 

 ment; and some have no tendon at either end. In many muscles 

 a tendon runs along one side and the fibers of the 

 belly are attached obliquely to it : such muscles 

 (B, Fig. 44) are called penniform or featherlike; 

 or a tendon runs obliquely down the middle of 

 the muscle and has the fibers of the belly fixed 

 obliquely on each side of it (C, Fig. 44) , forming 

 a bipenniform muscle: or even two tendons may 

 run down the belly and so form a tripenniform 

 muscle. In a few cases a tendon is found in the 

 iiiuttratin'" m iddle f the belly as well as at each end of it; 

 typical muscles with such muscles are called digastric. A muscle of 



a central belly and . . . . . . . . , 



two terminal ten- this form (Fig. 45) is found in connection with 

 fl3 rmmuscie;c, e abi: the lower Jaw. It arises by a tendon attached 

 penniform muscle, to the base of the skull; from there its first belly 

 runs downwards and forwards to the neck by the side of the 

 hyoid bone, where it ends in a tendon which passes through a 

 loop serving as a pulley. This is succeeded by a second belly di- 

 rected upwards towards the chin, where it ends in a tendon in- 

 serted into the lower jaw. Running along the 

 front of the abdomen from the pelvis to the chest 

 is a long muscle on each side of the middle line 

 called the rectus abdominis: it is poly gastric, con- 

 sisting of four bellies separated by short tendons. 

 Many muscles moreover are not rounded but form gastric muscle, 

 wide flat masses, as for example the muscle Ss seen on the ventral 

 side of the shoulder-blade in Fig. 42. 



Gross Structure of a Muscle. However the form of the skeletal 

 muscles and the arrangement of their tendons may vary, the 

 essential structure of all is the same. Each consists of a proper 



FIG. 

 grams 



FIG. 45. A di- 



