FLEXOR DIVISION 



269 



Origin. — The extensor (external) epicondyle of the humerus, behind and below 

 the lateral ligament. 



Insertion. — (1) The outer surface and upper edge of the accessory carpal 

 bone; (2) the proximal extremity of the outer (fourth) metacarpal bone. 



Action. — To fiex the carpal joint and to extend the elbow. 



Structure. — The belly of the muscle is flattened and is intersected by a good 

 deal of tendinous tissue. There are tw^o tendons of insertion. The short tendon 

 is inserted into the accessory carpal bone. The long tendon is detached just above 

 the carpus; it is smaller and rounded; it passes downward and a little forward 

 through a groove on the outer surface of the accessory carpal bone, enveloped by 

 a synovial sheath, to reach its insertion on the outer metacarpal bone. A synovial 



For tendon of 

 anterior extensor 



For tendon of ex- 

 tensor carpi radialis 



Joint cavity 



For tendon of lateral 

 extensor 



External lateral liga- 

 ment 



For long tendon of 

 flexor carpi externus 



Posterior annular 

 ligament 



Infernal meta- 

 carpal nerve in 

 carpal canal 



For tendon of extensor 

 carpi ohliquus 



Bursa 



Internal lateral liga- 

 ment 



Posterior ligament of 

 carpus 



For tendon of flexor carpi 



internus 



Large metacarpal artery 



Internal metacarpal vein 



Fig. 194.— Cross-section of Proximal Part of Left Carpus of Horse. 

 The tendons have been removed to show the canals in which they lie. The joint cavity is black. 



By 



an over.sight the carpal canal for the two flexor tendons behind the jjosterior liganaent of the carpus is not marked. 

 Cr, Radial, Ci, intermediate, Cu, ulnar, Ca, accessory carjjal bones. 



pouch lies under the origin of the muscle at the ell^ow joint, with the cavity of 

 which it communicates. 



Relations. — Superficially, the skin, fascia, and cutaneous branches of the ulnar 

 nerve; deeply, the ell)ow joint, the ulna, and the flexors of the digit; in front, the 

 lateral extensor of the digit; behind, the middle flexor of the carpus, the ulnar head 

 of the deep flexor, and the ulnar vessels and nerve. 



Blood-supply. — Interosseous, ulnar, and median arteries. 



Nerve-supply. — Radial nerve. 



4. Superficial digital flexor or flexor perforatus (M. flexor digitalis sublimis; 

 superficial flexor of the phalanges) . — This muscle is situated in the middle of the 

 flexor group, chiefly under cover of the middle flexor of the carpus. 



Origin. — (1) The flexor epicondyle of the humerus, between the flexor carpi 

 internus and the deep flexor of the digit; (2) a ridge on the posterior surface of the 

 radius, below its middle and near the internal border. 



Insertion. — (1) The eminences on the proximal extremity of the second phalanx 



