THE MEDIAN ARTERY 



657 



interossea dorsalis) descends between the comfhon 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. 



— Tendon of common extetisor 



Mc. II 



Common digital vein 

 Common digital artery 

 Medial volar nerve 

 Superficial flexor tendon 



Tcir^u/i of lateral extensor 



yy^Mc. ir 



^ 11 'S - Suspensory ligament 



Lateral volar metiicnrpal 



vessel 



Lateral volar nerve 



Check ligament 

 ^Deep flexor tendon 

 Deep fascia 



Fig. 571. — Cross-section of Right Metacarpus of Horse. 



Section is cut a little above middle of region. 



1, 1', Dor.sal 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 



^ Also termed the external metacarpal artery. 

 2 Also called the internal or small metacarpal artery. 

 42 



