THE POPLITEAL ARTERY POSTERIOR TIBIAL ARTERY 581 



between the adductor (in front) and the semimembranosus (liehind), and enters 

 the biceps femoris, in which it ramifies. The descencUng branch passes downward 

 and backward on the external head of the gastrocnemius, then curves upward be- 

 tween the biceps femoris and semitendinosus (crossed externally by the tibial 

 nerve) and divides into branches to these muscles. A branch is detached from 

 the convexity of the curve which passes down between the heads of the gas- 

 trocnemius, gives branches to that muscle and the flexor perforans, and is con- 

 tinued by a slender artery which accompanies the tibial nerve and unites with 

 the recurrent tibial artery. A branch ascends alongside of the sciatic nerve be- 

 tween the biceps and semitendinosus and anastomoses with a descending branch 

 of the obturator. 



The Popliteal Artery 

 This artery (A. poplitea) is the direct continuation of the femoral. It lies 

 between the two heads of the gastrocnemius, at first on the posterior face of the 

 femur, then on the femoro-tibial joint capsule. It then passes down through the 

 popliteal notch under cover of the popliteus, inclines outward, and divides near the 

 upper part of the interosseous space into anterior and posterior tibial arteries. 

 The satellite vein lies along its inner side. Collateral branches are supplied to the 

 stifle joint and the gastrocnemius and popliteus. 



posterior TIBIAL ARTERY 



The posterior tibial artery (A. tibialis posterior) is much the smaller of the two 

 terminals of the popliteal. It lies at first between the tibia and the popliteus, 

 then between that muscle and the deep and inner heads of the deep flexor. Lower 

 down it descends along the tendon of the inner head, becomes superficial in the 

 distal third of the leg, and passes behind the tendon. At the level of the tuber 

 calcis it forms an C/D-shaped curve, runs downward along the deep flexor tendon 

 accompanied by the plantar nerves, and divides at the lower part of the hock into 

 internal and external plantar arteries. The collateral branches are as follows: 



1. The nutrient artery of the tibia (A. nutritia tibiae). 



2. Muscular branches (Rami musculares) to the popliteus and deep flexor. 



3. The external tarsal artery (A. tarsea lateralis) arises at the distal end of the 

 leg and is distributed to the outer surface of the hock. It gives off a small recur- 

 rent branch which ascends along the external border of the gastrocnemius tendon 

 and anastomoses with a branch of the posterior femoral artery. 



4. The recurrent tibial artery (A. tibialis recurrens) is given off from the second 

 part of the curve, ascends in relation to the tibial nerve, and anastomoses with the 

 descending branch of the posterior femoral and with the saphenous artery. 



5. Small branches (internal calcaneal) to the inner aspect of the hock. 



6. The plantar arteries, internal and external (A. plantaris medialis, lateralis), 

 are the small terminals of the posterior tibial. They descend along the sides of 

 the tarsal sheath of the deep flexor with the plantar nerves to the proximal part of 

 the metatarsus, where they unite with the perforating tarsal artery to form the 

 plantar arch (Arcus plantaris). Four plantar metatarsal arteries proceed from this 

 arch. The two slender superficial plantar metatarsal arteries (A. metatarsea plan- 

 taris superficialis medialis, lateralis) descend on either side of the deep flexor tendon 

 with the plantar nerves and unite with the great metatarsal or with the corre- 

 sponding digital artery. The two deep or interosseous plantar metatarsal 

 arteries (A. metatarsea plantaris profundus medialis, lateralis) descend between 

 the suspensory ligament and the corresponding small metatarsal bone and unite 

 near the fetlock with the great metatarsal. The inner artery is the larger of the 



