592 THE ARTERIES 



where it gives off a large branch, the anterior peroneal, and then, passing over the 

 back of the inferior tibio-fil)ular joint, terminates by breaking up into a network, 

 Avhich is distributed over the back of the external malleolus and outer surface of 

 the calcaneum (tig. 381). It is accompanied by two vena? comites. 



Relations. — At its upper part it is deeply placed between the tibialis posticus 

 and soleus muscles, and beneath the deep or intermuscular fascia. For the rest of 

 its course to the ankle it lies beneath, or sometimes in the substance of the flexor 

 longus hallucis in the angle between the fibula and interosseous membrane. After 

 giving off the anterior peroneal, it is only covered, as it lies behind the tibio-fibular 

 articulation, by the integuments and deep fascia, and in this part of its course is 

 sometimes called the posterior peroneal. 



The branches of the peroneal artery are: — (a) The anterior peroneal; (6) the 

 muscular; (c) the medullary; i^d) the communicating; (e) the cutaneous; (/) the 

 external calcanean; and (g) the terminal. 



(a) The anterior peroneal artery arises from the front of the peroneal artery 

 at the lower part of the interosseous space, and, passing through the interosseous 

 membrane, runs downwards over the front of the inferior tibio-fibular joint, beneath 

 the peroneus tertius, and supplies this muscle and the inferior tibio-fibular joint. It 

 anastomoses with the tarsal, metatarsal, and external malleolar branches of the 

 anterior tibial artery, and with the external plantar artery on the outer side of the 

 foot, forming a plexus over the outer ankle (fig. 380). 



(6) The muscular branches of the peroneal artery are distril)uted to the con- 

 tiguous muscles, namely: the flexor longus hallucis, the tibialis posticus, the 

 peronei, and the soleus. 



(c) The medullary enters the nutrient foramen of the fibula. 



(cZ) The communicating branches pass transversely inwards in front of the 

 tendo Achillis to anastomose with the communicating branch of the posterior 

 tibial. The usual situation of this communication is from one to two inches above 

 the ankle-joint. 



(e) The cutaneous branches run outwards between the flexor longus hallucis 

 and soleus to supply the integuments on the outer side of the leg. 



(/) The external calcanean comes off from the peroneal below the point at 

 which the anterior peroneal is given off, and is distributed over the outer surface of 

 the OS calcis. 



(gr) The terminal branch or posterior peroneal, the continuation of the 

 peroneal artery, anastomoses with the other arteries distributed to the external 

 malleolus and heel. 



(2) The muscular branches of the posterior tibial artery are distributed to the 

 contiguous muscles, namely: the tibialis posticus, flexor longus digitorum, and 

 soleus. 



(3) The medullary artery, a vessel of large size, leaves the posterior tibial at 

 its upper part, pierces the tilnalis posticus, and enters the medullary foramen in 

 the upper third of the posterior surface of the tibia. In the interior of the bone 

 it divides into two branches: an ascending or smaller, which runs upwards towards 

 the head of the bone; and a descending or larger, Avhich courses downwards 

 towards the lower end. It gives off two or three muscular twigs to the tibialis 

 posticus before it enters the' foramen. The medullary artery of the tibia is the 

 largest nutrient artery of bone in the body, and is accompanied by a nerve given 

 off liy the nerve to the popliteus. 



(4) The cutaneous branches ]»ass inwards to the integuments on the inner 

 side of the leg. They run in the cellular planes between the deep and superficial 

 muscles, and serve as useful guides to tlie vessel Avhen ligaturing the posterior 

 tibial through the lateral incision. 



(5) The communicating branch arises from the posterior tibial aliout two 

 indies above tlie inner malleolus, and, ])assing transversely outwards across the 

 tibia beneath the flexor longus hallucis and tendo Achillis, anastomoses with the 

 communicating branch of the peroneal. 



Frequently an inferior communicating branch between the posterior tibial and 

 peroneal arteries is likewise present in the loose connective tissue beneath or behind 

 the tendo Achillis (fig. 374). 



