498 THE ARTERIES OF THE LOWER LIMB. 



(d) The anterior per oneal artery (v), arising from an inch to an inch and a half 

 above the ankle-joint, passes forwards below the interosseous membrane, and descends 

 in front of the articulation between the tibia and fibula to the outer side of the 

 tarsus. It communicates with the external malleolar branch of the anterior tibial 

 artery, and supplies offsets to the peroneus terfcius muscle and the articulations of 

 the ankle ; its terminal branches anastomose with the posterior peroneal and tarsal 

 arteries. 



(e) The terminal branches of the posterior peroneal artery (external calcaneal} 

 anastomose with the external malleolar and tarsal arteries on the outer side 

 of the foot, and over the heel with the internal calcaneal branches of the external 

 plantar artery. 



Varieties. The posterior tiMal artery, as well as the anterior tibial, is lengthened in 

 those instances in which the popliteal artery divides higher up than usual. Not unfrequently 

 the posterior tibial artery is diminished in size, and is subsequently reinforced, either by a 

 transverse branch from the peroneal in the lower part of the leg, or, more rarely, by 

 two transverse vessels, one crossing close to the bone, and the other over the deep muscles. 

 In other instances the posterior tibial may exist only as a short muscular trunk in the upper 

 part of the leg, or may be entirely wanting, while an enlarged peroneal artery takes its place 

 from above the ankle downwards into the foot. One or two internal calcaneal branches 

 (v. p. 600) are frequently given off from the lower end of the posterior tibial artery. 



The posterior tibial artery is occasionally covered in the lower third of the leg by muscle, 

 which may be an accessory long flexor of the toes (p. 265), or a slip of the soleus (p. 264). 



The peroneal artery has been found to arise lower down than usual, about three inches 

 below the popliteus muscle ; and, on the contrary, it sometimes arises higher up from the 

 posterior tibial, or even from the end of the popliteal artery. In some cases of high division 

 of the popliteal artery, the peroneal artery is transferred to the anterior tibial. It more 

 frequently exceeds than falls short of the ordinary dimensions, being enlarged to reinforce 

 the posterior tibial. In those rare instances in which it is lost before reaching the lower part 

 of the leg, a branch of the posterior tibial takes its place. Absence of the peroneal artery has 

 been recorded by Otto and W. Krause, but these cases are explained by Barkow. as being 

 correctly suppression of the posterior tibial artery between the origin of the peroneal and the 

 communicating branch. The anterior peroneal branch is sometimes enlarged to compensate 

 for the small size of the anterior tibial artery in the lower part of the leg, or to supply the 

 place of that artery on the dorsum of the foot ; or it may be absent and be replaced by the 

 external malleolar branch of the anterior tibial. 



PLANTAR ARTERIES. 



The internal and external plantar arteries are the branches into which the pos- 

 terior tibial divides, immediately below the internal annular ligament, where it is 

 covered by the origin of the abductor hallucis muscle. 



The internal plantar artery (v), much smaller than the external, lies along 

 the inner side of the foot. Placed at first under cover of the abductor hallucis, it 

 passes forwards in the interval between that muscle and the short flexor of the toes, 

 and on reaching the head of the first metatarsal bone, considerably diminished 

 in size, it terminates by joining the digital artery to the inner side of the great 

 toe. 



Branches. (a) Small branches of this artery accompany the digital branches of 

 the internal plantar nerve, and join the digital arteries in the inner three clefts. It 

 also gives (&) offsets to the surrounding muscles, and (c) cutaneous branches, which 

 appear in the furrow between the middle and internal portions of the plantar fascia. 

 (d) Other branches pass inwards and appear at the upper border of the abductor 

 hallucis muscle, supplying the integument and anastomosing with offsets of the 

 dorsal artery of the foot ; and (e) from the outer side one or more branches run 

 deeply into the foot, to supply the articulations and anastomose with branches of the 

 plantar arch. 



The external plantar artery (iv) at first inclines outwards and forwards, to 



