346 ZOOTOMY. 



elbow-joint : it arises from the inner condyle of the humerus, 

 and is inserted into the olecranon. 



413. The biceps brachii (hi), or chief flexor of the 

 fore-arm : a spindle-shaped muscle forming the anterior 

 edge of the upper arm: it arises by a single cord-like 

 tendon, working in the bicipital groove of the humerus, 

 from the anterior edge of the glenoid cavity, and is in- 

 serted into the proximal end of the radius : cut it through 

 and reflect. 



414. The brachialis internus {br.i), a flattish muscle 

 lying on the outer face of the upper arm between the an- 

 coneus brevis and the biceps : it arises from the outer 

 surface of the proximal portion of the shaft of the humerus 

 and is inserted into the radius just proximal to the insertion 

 of the biceps 



In the fore-arm and liand. 



415. The extensor carpi radialis (Figs. 65, A and C, 

 and 66, ex.cf.r), or chief extensor of the entire hand, a long 

 muscle forming the anterior edge of the fore-arm : it arises 

 from the outer condyle of the humerus : its distal end divides 

 into the slender tendons which pass beneath the tendon 

 of the abductor pollicis (§ 418), and then under the annu- 

 lar ligament {a?i.l), a. transverse fibrous band at the junc- 

 tion of the fore-arm and hand, and are inserted into the 

 proximal ends of the second and third metacarpals : cut 

 through and reflect. 



416. The extensor communis digitorum (ex.c.d), or 

 principal extensor of the fingers, a long muscle situated on 

 the external and dorsal surface of the fore-arm in the groove 

 between the radius and ulna : it arises from the outer con- 

 dyle of the humerus, and at the distal end of the fore-arm 

 divides into four tendons which pass beneath the annular 

 ligament to the four post-axial digits. Each tendon passes 



