THE VEINS 



79 



ascends across the lateral aspect of the fetlock. Just above this joint the 

 two veins converge towards the middle line, where they unite and thus 

 form a venous arch which is disposed transversely, and which is placed 

 between the suspensory ligament and the tendon of the flexor 

 perforans. 



The Metacarpal Veins. — From the venous arch described above three 

 veins are given off. These are termed respectively the internal, external, 

 and deep metacarpal veins. 



The Internal Metacarpal Vein. — This is the most voluminous of the 

 three veins which leave the arch. It ascends the limb in front of the 

 large metacarpal artery, being at first placed on the inner edge of the 

 perforans tendon. It then inclines slightly forwards, crosses the internal 

 dorsal interosseous artery, and leaves the tendons, large metacarpal artery, 

 &c., at the inferior opening of the carpal sheath, since the vein does not 

 pass through the sheath. It is next found on the inner aspect of the 

 knee superficially to the fibrous carpal arch, where it is placed in front of 

 the small metacarpal artery. In the region of the forearm it is con- 

 tinued as the internal subcutaneous vein. 



The External Metacarpal Vein. — This vein appears on the outer edge 

 of the perforans tendon in the inferior third of the metacarpal region. 

 It ascends along the outer edge of the tendon in front of the external 

 plantar nerve, but in the upper part of the metacarpal region the outer 

 small unnamed artery, which descends for a varying distance down the 

 metacarpus, is insinuated between the nerve and vein. At the carpus the 

 vein splits up into a number of vessels which form an intricate plexus 

 which is drained by the ulnar and posterior radial veins. 



The Deep Metacarpal Vein. — This is frequently termed the interosseous 

 metacarpal vein. It has a very tortuous disposition, and is not infrequently 

 double. It usually ascends from the arch between the edge of the sus- 

 pensory ligament and the inner small metacarpal bone, ultimately splitting 

 up into a number of vessels, some of which assist in the formation of 

 the carpal plexus, whilst the remainder join the internal metacarpal vein. 



