THE VEINS 719 



of the saphenous. It descends along the medial border of the superficial flexor 

 tendon and divides into medial and lateral plantar arteries. The medial plantar 

 artery descends along the medial side of the deep flexor tendon with the medial 

 plantar nerve. It anastomoses at the proximal end of the metatarsus with the 

 perforating tarsal artery, assisting in the formation of the proximal plantar 

 arch, and continues distally as the a. met. plant, superfic. med. along the medial 

 border of the deep flexor tendon. Near the fetlock it concurs with the perforating 

 branch of the dorsal metatarsal artery and with a branch of the corresponding 

 lateral artery in the formation of the distal plantar arch. Below this it is continued 

 as the medial digital artery. The lateral plantar artery is small.^ It descends 

 along the lateral border of the deep flexor tendon with the lateral plantar nerve, 

 concurs with the perforating tarsal and medial plantar arteries in the formation 

 of the proximal plantar arch, and gives branches to the rete tarsi dorsale. Continu- 

 ing downward along the deep flexor tendon as the a. met. plant, superfic. lat., it 

 assists in forming the distal plantar arch and becomes the lateral digital artery. 



The posterior tibial artery is relatively small and is distributed chiefly to the 

 muscles on the posterior surface of the tibia. Lower down it is replaced by the 

 saphenous artery, as described above. 



The anterior tibial artery has the same course as in the horse. It is continued 

 down the groove on the front of the metatarsal bone as the dorsal metatarsal artery. 

 At the tarsus branches are given off which concur with the lateral tarsal artery in 

 the formation of the rete tarsi dorsale. The perforating tarsal artery passes back 

 through the vascular canal and anastomoses with the plantar arteries, thus forming 

 the proximal plantar arch. From this the small deep plantar metatarsal artery 

 descends in the plantar groove of the large metatarsal bone to the distal plantar 

 arch. The dorsal metatarsal artery (A. met. dorsalis) is the chief artery of the 

 region and is accompanied by two veins. Near the distal end of the metatarsal 

 bone it gives off the perforating metatarsal artery, which passes back through the 

 distal metatarsal foramen and assists in forming the distal plantar arch. 



The dorsal common digital artery is the direct continuation of the dorsal 

 metatarsal. It divides into two branches which unite in the interdigital space with 

 the corresponding branches of the plantar common digital to form the proper 

 digital arteries. 



The plantar common digital artery descends from the distal plantar arch, 

 anastomoses in the interdigital space with the medial and lateral digitals, and 

 divides into two branches which join those of the dorsal common digital artery as 

 before mentioned. 



The foregoing is a brief statement of the more common arrangement of the 

 vessels in the distal part of the limb, but minor variations are very common. 



The Veins 2 



The vena hemiazygos takes the place of the vena azygos. It lies along the 

 left side of the aorta and the bodies of the thoracic vertebrae, turns down across 

 the left face of the aorta and left pulmonary artery, runs back over the left auricle, 

 and usually joins the great cardiac vein, but may open into the right atrium. It 

 receives the dorsal intercostal veins. 



Two jugular veins occur on either side. The internal jugular vein (V. jugu- 

 laris interna) is a relatively small vessel which accompanies the carotid artery. It 



1 This vessel may arise instead from the rete tarsi dorsale. 



2 Most of the differences in the veins of the ox are correlated with those of the arteries of 

 which they are satellites, and will not be described. The account here given consists chiefly of 

 those differential features which could not be deduced from a knowledge of the arteries. 



