I20 THE SURGICAL ANATOMY OF THE HORSE 



cunean canal the large metatarsal artery passes downwards, outwards, and 

 backwards beneath the extensor brevis and the tendon of the peroneus, 

 at first on the large metatarsal bone, and then down the groove formed 

 between the large and external small metatarsals. 



The posterior tibial artery makes its appearance on the inner aspect 

 of the limb just above the hock and a short distance in front of 

 the posterior tibial nerve. It forms the peculiar, S-shaped curve, to 

 which reference has already been made, and then disappears within the 

 fibrous tarsal arch, dividing at the back of the astragalus into the two 

 plantar arteries which help to form the tarsal arterial arch. This arch 

 runs across the upper extremity of the suspensory ligament. The 

 posterior tibial artery gives off a number of collateral articular branches 

 to the tarsus. Small articular tarsal branches are also given off by the 

 plantar arteries. 



The internal metatarsal vein is continued upwards as the anterior root 

 of the internal saphena vein. This root inclines slightly forwards and 

 upwards, to become placed towards the front of the inner aspect of 

 the hock. Here it communicates with the anterior tibial vein, and 

 is then continued up the leg on the inner (subcutaneous) surface of 

 the tibia. 



The external metatarsal vein communicates with the deep metatarsal 

 vein at the upper end of the metatarsal region, and then runs upwardly 

 through the tarsal sheath with the plantar arteries. It forms the posterior 

 root of the internal saphena vein. This root also communicates with the 

 external saphena vein which begins at the calcis, through a large net- 

 work of veins which runs across the front of the tuber calcis. The deep 

 metatarsal vein runs upwards between the suspensory ligament and the 

 large metatarsal bone. At the tarsus it communicates with the external 

 metatarsal vein, and it then passes forwards through the canal formed 

 between the cuboid, scaphoid and cuneiform magnum, to reach the 

 front of the hock, where it forms the principal root of the anterior 

 tibial vein. 



