346 ZOOTOMY. 



elbow-joint : it arises from the inner condyleof the humerus, 

 and is inserted into the olecranon. 



413. The biceps brachii (/), 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 



/// the fore-arm and hand. 



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

 and 66, ex.cp.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 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 



