CHAP. VI.] 



THE MUSCLES. 



67 



Muscles of the upper extremity. 

 A certain number of muscles 

 situated superficially on the trunk 

 pass to the bones of the shoulder 

 and of the arm, so as to attach 

 the upper limbs to the trunk. Of 

 these, the two superficial muscles 

 we have mentioned as covering 

 the back, the trapezius and latis- 

 simus dorsi, and pectoral muscles 

 covering the front of the chest, 

 are the chief. The most promi- 

 nent muscles found in the upper 

 limbs are : 



Deltoid. 



Biceps. 



Triceps. 



Pronators. 

 Supinators. 

 Flexors. 

 Extensors. 



The deltoid is a coarse triangu- 

 lar muscle covering the top of 

 the shoulder; it extends down- 

 wards and is inserted into the 

 middle of the shaft of the hu- 

 merus. It raises the arm from the 

 side so as to bring it at right 

 angles to the trunk. 



The biceps is a long fusiform 

 muscle, occupying the whole of 

 the anterior surface of the arm ; 

 it is divided above into two 

 portions or heads, from which 

 circumstance it has received its 

 name. It arises by these two 

 heads from the shoulder-joint, 

 and is inserted into the radius. 



It flexes the forearm on the arm. 



FIG. 59. MUSCLES IN FRONT OF 

 ihe triceps is situated on the FOREARM. 6i>, proimtor tores :<;:;.;:.. 



back of the arm, extending- the (;<i > (57 flexors; 70, supinator i- 



. 71. 77, 78, extensors: </, annular nga- 



whole length of the posterior sur- mellt . 



