MEDIAN NERVE 



699 



epicondyle of the humerus. In the forearm it crosses obliquely the deep face of the 

 ulnar head of the flexor carpi medius and descends under the deep fascia with the 

 vessels, at first on the ulnar head of the perforans, and then between the middle and 

 external flexors of the carpus. Near the level of the accessory carpal bone it divides 

 into two terminal branches, sujierficial and deep. It gives off two principal col- 

 lateral l)ranches. The cutaneous branch (Ramus cutaneus palmaris) is detached 

 just before the nerve passes under the tensor fasciae antibrachii; it runs downward 

 and backward on that nmscle under cover of the posterior superficial pectoral, 

 becomes superficial below the elbow and ramifies on the posterior surface and both 

 sides of the forearm. The muscular branch is given off at the elbow joint and 

 divides to supply the flexors of the digit and the middle flexor of the carpus. Of 



Extensor carpi radialis 



Intermuscular septum 



A n lerior extensor of digit 



Intermuscular septum 



Lateral extensor of digit 



Inter muscular sept u m ' 



Flexor carpi extemus 

 Flexor per for an 

 {humeral head) 



Flexor perforatus 



Flexor perforans {ulnar head) 



Accessory cephalic vein 



t ; . . . | / — Vein 



Cephalic vein 



Internal lateral ligament 



of elbow 

 Median nerve 

 Posterior radial veins 

 Posterior radial artery 



Flexor carpi internus 



Flexor carpi medius 



Ulnar vein / Ulnar nerve 

 Ulnar artery 



Fig. 521. — Cross-section of Fokearm of Horse about Three Inches (ca. 8 cm.) below the Elbow Joint. 

 The deep fascia is designated by red line. N, A V, Interosseous ve.ssels and nerve. 



the two terminals, the superficial branch (Ramus superficialis) emerges between the 

 tendons of insertion of the external and middle flexors of the carpus and ramifies 

 on the dorso-lateral aspect of the carpus and metacarpus. The deep branch (Ramus 

 profundus), after a very short course, unites under cover of the tendon of the flexor 

 carpi medius with the outer branch of the median nerve to form the external meta- 

 carpal or volar nerve. 



Median Nerve 



The median nerve (Figs. 441, 442, 447, 520, 521) derives its fibers chiefly from 



the first thoracic root of the brachial plexus. It is usually the largest branch and 



it accompanies the chief arterial trunks to the distal part of the limb. It descends 



over the inner face of the brachial artery, which it crosses obliquely, and continues 



