THE LIMBS OF THE HOUSE 65 



(1) Rami dorsales phalangis primce. — On a level with the middle 

 of the first phalanx a dorsal branch arises from each digital artery 

 and passes between the common extensor tendon and the bone. 

 (2) Rami volares 2Jhalangis primce. — At the same level as the fore- 

 going, volar branches take origin and encircle the digit beneath the 

 flexor tendons. Not infrequently the dorsal and volar rami arise from 

 a short common trunk, the artery of the first phalanx (a. phalangis 

 primte). (3) Aa. toricK, phalangis tertite. — Shortly distal to the pre- 

 ceding, small branches are given off by the digital arteries to be 

 distributed mainly in the digital torus. The remaining branches of 

 the digital arteries can only be examined properly during the dissection 

 of the contents of the hoof. They are : — (4) Rami dorsales phalangis 

 secundcv ; (5) rami volares phalangis secundo: ; (6) aa. coronales phalangis 

 terticc ; and (7) aa. dorsales j)halangis tcrtia'. 



Digital veins. — When the contents of the hoof come to be 

 examined, it will be found that the veins therein form a rich and 

 close-meshed network. From this spring two veins (vv. digitalis 

 medialis et lateralis) that accompany the digital arteries. It should 

 be noted that each digital vein is dorsal to {i.e. in front of) the 

 corresponding artery. 



Between the flexor tendons and the middle interosseous muscle, 

 and immediately proximal to the sesamoid bones, there is an anasto- 

 motic union of veins known as the volar venous arch (arcus venosus 

 volaris). Connected with the arch are the digital veins on the one 

 hand, and the veins of the metacarpus on the other. 



Veins of the metacarpus. — (1) Beginning at the volar venous 

 arch, the common digital (or medial metacarpal) vein (v. digitalis 

 communis) is a conipanion of the like-named artery. At the 

 carpus, however, its chief connection is with the origin of the 

 cephalic vein of the forearm, though it is also connected with the 

 median vein. (2) The lateral volar metacarpal vein (v. metacarpea 

 volaris lateralis) accompanies the artery of the same name to the 

 carpus. In this region it is connected with both the median and 

 the collateral ulnar veins. (3) The deep volar metacarpal vein (v. 

 metacarpea volaris profunda) is variable. Lying between the third 

 metacarpal bone and the interosseous muscle, its main connection 

 is with the median vein. 



Nerves of the metacarpus and digit. — At a variable point in 

 the distal half of the forearm the median nerve divides into two 

 terminal branches — the medial and lateral volar nerves. The 

 medial volar nerve (n. volaris medialis) follows the common digital 

 artery along the medial border of the flexor tendons down the back 



