818 



NERVOUS SYSTEM OF THE HORSE 



the tendon of the ulnaris lateraHs 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 



Medial metacarpal vein 



Volar nerve 



Digital artery 



Dorsal digital branch 

 Volar digital branch 



Corollary plexus 



Distal end of lateral small meta- 

 carpal bone 



Large metacarpal bone 

 Suspensory ligament 



— Superficial flexor tendon 



Posterior annular ligament of 

 fetlock 



Extensor branch of suspensory 



lifinment 



Oblique or middle distal 



sisamoidean ligament 



Volar ligament of pastern joint 



Proximal annular ligament of digit 



Dee p flexor tendon 



Dibtal annular ligament of digit 



Fig. 054. — Dissection of Distal Part of Right Fore Limb op Horse; Volar Surface. 



1, Cartilage of third phalanx; 3, 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 ligament. 

 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 radiaUs, 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. 



