200 THE SURGICAL ANATOMY OF THE HORSE 



branch from the posterior tibial nerve, it now forms a peculiar sigmoid 

 curve from before backwards, the first convexity of which is placed 

 anteriorly and is directed downwards. In this portion of its course the vessel 

 is found immediately beneath the deep fascia. From the second portion 

 of the curve its course is downwards in front of the tendo-Achilles, and in 

 close proximity to the posterior tibial nerve and its continuations, passing 

 with these through the tarsal sheath. Arriving at the back of the 

 astragalus, the vessel terminates by dividing into the two plantar 

 arteries. 



The branches of the posterior tibial artery are as follows : 



1. Numerous muscular branches are distributed to the deep layer 

 of muscles on the back of the tibia — namely, the flexor perforans, the 

 flexor accessorius, and the popliteus. 



2. The nutrient artery to the tibia. This is a very short branch which 

 leaves the posterior tibial artery near the line of apposition of the popliteus 

 and flexor perforans muscles. The artery enters the nutrient foramen, 

 which is placed on the posterior surface of the bone, near the line of 

 division between the area for the accommodation of the popliteus muscle 

 and the area from which the flexor perforans muscle arises. 



3. Articular branches are distributed to the hock joint. 



4. A retrograde branch is detached from the convexity of the posterior 

 portion of the sigmoid flexure. This branch ascends in front of the 

 tendo-Achilles in close proximity to the posterior tibial nerve and its 

 continuations. 



The anterior tibial artery is in intimate relationship to the tibia itself 

 almost throughout the whole of its course. It is deeply seated, and 

 protected from external injury by the muscles which cover it. It may, 

 however, be damaged in cases of severe fracture of the tibia, and hemor- 

 rhage from it may also arise as a result of deep punctured wounds received 

 over the front of the hock, where the artery divides into the perforating 

 metatarsal and large metatarsal arteries. 



The posterior tibial artery is well protected from external injury until 



