THE LOWER LIMB 5^3 



The artery is accompanied by the external plantar nerve through- 

 out its whole course, and by two venae comites. At its origin it is 

 situated on the inner surface of the os calcis, from which point it is 

 directed outwards and forwards across the sole to the base of the 

 fifth metatarsal bone. It here describes a sharp bend, and, sinking 

 deeply, it recrosses the sole on its way to the proximal part of the 

 first interosseous space. The vessel is divided into two parts, 

 first and second. These two parts together describe one great 

 curve, the concavity of which looks inwards and is occupied by the 

 external plantar nerve. 



The first part extends from the lower border of the internal 

 annular ligament to the base of the fifth metatarsal bone. Its 

 course may be indicated by drawing a hne from a point midway 

 between the tip of the internal malleolus and the inner tubercle on the 

 plantar aspect of the tuber calcis to the base of the fifth metatarsal 

 bone. The direction of this part is outwards and forwards. 



Relations. — It is covered in succession by the abductor hallucis, 

 flexor brevis digitorum, and finally only by the skin, superficial 

 fascia, and plantar fascia. It rests upon the os calcis and the 

 musculus accessorius. 



It is to be noted that this part of the vessel is very superficial for a 

 short distance close to the base of the fifth metatarsal bone, where it 

 lies between the flexor brevis digitorum and abductor minimi digiti. 



The second part extends from the base of the fifth metatarsal 

 bone to the proximal part of the first interosseous space. Its 

 course may be indicated by a line connecting the limits of this part 

 of the vessel. It is directed inwards and forwards in a slightly 

 curved manner, with the convexity of the cur\^e forwards, and thus 

 it forms the plantar arch, which is completed by the communicating 

 branch of the plantar division of the arteria dorsalis pedis. The 

 second part is accompanied by the deep division of the external 

 plantar nerve, and is very deeply placed. 



Relations. — It is covered by the skin, superficial fascia, central 

 division of the plantar fascia, flexor brevis digitorum, flexor longus 

 digitorum, lumbricales, and adductor obhquus hallucis. It rests 

 upon the bases of the second, third, and fourth metatarsal bones 

 cind the corresponding interosseous muscles. 



Branches of the First Part. — ^The branches are as follows : 



Muscular to the muscles in its immediate vicinity. 



The internal calcaneal branches are two or three in number. 

 After piercing the origin of the abductor hallucis, they reach the 

 inner surface of the os calcis, where they anastomose with the 

 internal calcaneal branch of the posterior tibial artery. Over the 

 prominence of the heel they also anastomose freely with the 

 external calcaneal branches of the posterior peroneal artery. 



Cutaneous to the integument of the outer half of the foot. 



Branches also turn round the outer border of the foot, where 

 they anastomose with the tarsal and metatarsal branches of the 

 arteria dorsalis pedis and with the posterior peroneal artery. 



