THE MEDIAN ARTERY 657 
interossea dorsalis) descends between the common and lateral extensors of the digit 
and concurs with the anterior radial in forming a network on the dorsal surface of 
the carpus, the rete carpi dorsale. From the latter arise two small vessels, the 
medial and lateral dorsal metacarpal arteries (A. metacarpea dorsalis medialis, 
lateralis), which run distally in the grooves between the large and small metacarpal 
bones and anastomose with the volar metacarpal arteries. 
4. The artery of the rete carpi volare (A. retis carpi volaris) is a small vessel 
which arises at the distal third of the forearm and descends on the radius to the 
posterior surface of the carpus, where it concurs with branches of the volar meta- 
carpal arteries in forming the rete carpi volare. 
5. The lateral volar metacarpal artery (A. metacarpea volaris lateralis)! is a 
small vessel which arises just above the carpus under cover of the flexor carpi 
ulnaris and anastomoses with the ulnar artery, forming the supracarpal arch. 
From the latter a branch descends with the lateral branch of the median nerve, 
_Mc. IV 
[ f Suspensory ligament 
Lateral volar metacarpal 
vessel 
Common digital vein Lateral volar nerve 
aa —— ck li ont 
Common digital artery Checkaingamen 
Deep flexor tendon 
Medial volar nerve __ Deep fascia 
Superficial flexor tendon 
Fie, 571.—Cross-section oF Ricut Meracarpus oF HORSE. 
Section is cut a little above middle of region. 
1, 1’, Dorsal metacarpal arteries; 2, 2’, deep volar metacarpal arteries; 3, deep volar metacarpal vein; 4, distal part of 
carpal sheath. 
inclines outward toward the posterior border of the accessory carpal bone, and 
arrives at the head of the lateral metacarpal bone. Here it is connected with the 
medial volar metacarpal artery, usually by two transverse branches, thus forming 
the deep volar or subcarpal arch (Arcus volaris profundus proximalis). One of 
these branches lies between the subcarpal check ligament and the suspensory 
ligament; the other (not always present) lies beneath the latter on the large meta- 
carpal bone. A small branch descends to the fetlock with the lateral volar nerve. 
Below the arch the artery pursues a flexuous course downward on the volar face of 
the large metacarpal bone alongside of the lateral small metacarpal and under 
cover of the suspensory ligament. At the distal third of the metacarpus it com- 
monly unites with the corresponding vessel of the other side to form a short trunk 
which passes backward through the angle of divergence of the branches of the sus- 
pensory ligament and joins the lateral digital or the common digital artery. This 
junction forms the distal volar arch (Arcus volaris distalis). 
6. The medial volar metacarpal artery (A. metacarpea volaris medialis)* is 
1 Also termed the external metacarpal artery. 
2 Also called the internal or small metacarpal artery. 
42 
