588 THE BLOOD-VASCULAR SYSTEM. 



space, as the artery divides in that situation. The deep fascia being divided to the same extent, 

 the artery will be exposed, the nerve lying upon its outer side. 



Branches. The branches of the dorsalis pedis are the 



Tarsal. Dorsalis Hallucis. 



Metatarsal Interosseous. Communicating. 



The tarsal artery arises from the dorsalis pedis, as that vessel crosses the navic- 

 ular bone ; it passes in an arched direction outward, lying upon the tarsal bones, 

 and covered by the Extensor brevis digitorum ; it supplies that muscle and the 

 articulations of the tarsus, and anastomoses with branches from the metatarsal, 

 external malleolar, peroneal, and external plantar arteries. 



The metatarsal arises a little anterior to the preceding ; it passes outward to 

 the outer part of the foot, over the bases of the metatarsal bones, beneath the ten- 

 dons of the short Extensor, its direction being influenced by its point of origin ; 

 and it anastomoses with the tarsal and external plantar arteries. This vessel 

 gives off three branches, the interosseous arteries, which pass forward upon the 

 three outer Dorsal interossei muscles, and, in the clefts between the toes, divide 

 into two dorsal collateral branches for the adjoining toes. At the back part of 

 each interosseous space these vessels receive the posterior perforating branches 

 from the plantar arch, and at the fore part of each interosseous space they are 

 joined by the anterior perforating branches from the digital arteries. The outer- 

 most interosseous artery gives off a branch which supplies the outer side of the 

 little toe. 



The dorsalis hallucis (first dorsal interosseous) runs forward along the outer 

 border of the first metatarsal bone, and at the cleft between the first and second 

 toes divides into two branches, one of which passes inward, beneath the tendon of 

 the Extensor proprius hallucis, and is distributed to the inner border of. the great 

 toe ; the outer branch bifurcates, to supply the adjoining sides of the great and 

 second toes. 



The communicating artery dips down into the sole of the foot, between the two 

 heads of the First dorsal interosseous muscle, and inosculates with the termination 

 of the external plantar artery, to complete the plantar arch. It here gives off its 

 plantar digital branch, which is named the arteria magna hallucis. This artery 

 passes forward along the first interosseous space, and, after sending a branch along 

 the inner side of the great toe, bifurcates for the supply of the adjacent sides of the 

 great and second toes. 



The Posterior Tibial Artery. 



The posterior tibial is an artery of large size, which extends obliquely down- 

 ward from the lower border of the Popliteus muscle, along the tibial side of the 

 leg, to the fossa between the inner ankle and the heel, where it divides beneath 

 the origin of the Abductor hallucis, on a level with a line drawn from the point of 

 the internal malleolus to the centre of the convexity of the heel, into the internal 

 and external plantar arteries. At its origin it lies opposite the interval between 

 the tibia and fibula ; as it descends, it approaches the inner side of the leg, lying 

 behind the tibia, and, in the lower part of its course, is situated midway between 

 the inner malleolus and the tuberosity of the os calcis. 



Relations. It lies successively upon the Tibialis posticus, the Flexor longus 

 digitorum, the tibia, and the back part of the ankle-joint. It is covered by the 

 deep transverse fascia, which separates it above from the Gastrocnemius and 

 Soleus muscles : at its termination it is covered by the Abductor hallucis muscle. 

 In the lower third, where it is more superficial, it is covered only by the integ- 

 ument and fascia, and runs parallel with the inner border of the tendo Achillis. 

 It is accompanied by two veins and by the posterior tibial nerve, which lies at 

 first to the inner side of the artery, but soon crosses it, and is, in the greater part 

 of its course, on its outer side. 



