818 NERVOUS SYSTEM OF THE HORSE 
the tendon of the ulnaris lateralis with the lateral branch of the median nerve to 
form the lateral volar nerve. 
MEDIAN NERVE 
The median nerve (Figs. 566, 567, 572, 652, 653) derives its fibers chiefly from 
the eighth cervical and first thoracic roots 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 medial face of the brachial artery, which it crosses 
obliquely, and continues down the arm in front of the artery. Near its origin it is 
Distal end of lateral small meta- 
Medial metacarpal vein carpal bone 
a Large metacarpal bone 
Volar nerve 
Suspensory ligament 
Digital artery 
Superficial flexor tendon 
Posterior annular ligament of 
fetlock 
Extensor branch of suspensory 
ligament 
Oblique or middle distal 
sesamoidean ligament 
Volar ligament of pastern joint 
Dorsal digital branch — 
Volar digital branch 
Proximal annular ligament of digit 
Deep flexor tendon 
Distal annular ligament of digit 
Fic. 654.—Dissection oF Distat Part oF Ricut Fore Limp or Horse; VoLAR SURFACE. 
1, Cartilage of third phalanx; 2, 3, 4, ligaments from first phalanx to distal sesamoid, bulb of heel and cartilage of third 
phalanx. (After Schmaltz, Atlas d. Anat. d. Pferdes.) 
joined by a large branch with the musculo-cutaneous nerve, thus forming a loop in 
which the artery appears to be suspended. Near the elbow it usually crosses 
obliquely over the median artery and lies behind it on the medial lgament. 
Below the joint it again crosses the artery and lies behind the radius and the 
lower part of the long medial ligament. 
At the elbow the nerve is covered by the posterior superficial pectoral muscle and is crossed 
by the large oblique connection between the cephalic and brachial veins. The variable and often 
plexiform venous arrangement renders approach to the nerve here undesirable. It can be reached 
best by an incision just behind the lower part of the long medial ligament; here the nerve 
lies under the deep fascia in the furrow between the radius and the anterior border of the flexor 
carpi radialis, overlapped by the latter. Not uncommonly the nerve retains its position in front 
of the artery at the elbow; in other cases it lies upon the artery, and rarely it crosses the deep face 
of the artery. 
