500 THE ARTERIES OF THE LOWER LIMB. 



middle from the external portion of the plantar fascia, and covered by that mem- 

 brane. The remainder of the artery, which turns inwards and forms the plantar 

 arch, is placed deeply against the interosseous muscles, and is covered by the flexors 

 of the toes, the lumbricales muscles, and the adductor obliquus hallucis. 



Branches. A. In its course to the fifth metatarsal tone, the external plantar 

 artery gives off (a) two or three internal calcaneal branches, which pierce the origin 

 of the abductor hallucis muscle and ramify over the heel, anastomosing with the 

 external calcaneal branches of the peroneal artery ; (b) numerous muscular branches ; 

 (c) small offsets which ascend over the outer border of the foot and anastomose with 

 the tarsal and metatarsal branches of the dorsal artery ; and (d) cutaneous offsets, 

 which appear in the groove between the middle and outer divisions of the plantar 

 fascia. 



B. From the plantar arch are given off the following branches : 



(a) From the concavity of the arch small offsets pass backwards to the articulations 

 of the tarsus, and anastomose with the deep branches of the internal plantar artery. 



(Z>) The posterior* perforating branches, three in number, pass upwards through 

 the back part of the three outer intermetatarsal spaces, between the heads of the 

 dorsal interosseous muscles, and on reaching the dorsum of the foot inosculate with 

 the interosseous branches of the metatarsal artery. 



(c) The digital branches (v) are four in number. The first digital artery inclines 

 outwards from the outermost part of the plantar arch, over the fifth metatarsal bone, 

 and runs along the outer border of the little toe. The second digital artery passes 

 forwards along the fourth intermetatarsal space, and near the cleft between the 

 fourth and fifth toes divides into two collateral branches, which course along the 

 contiguous borders of those toes. The third digital branch is similarly distributed 

 to the fourth and third toes, and the fourth to the third and second toes. 



The digital artery which supplies the opposed sides of the first and second toes, 

 and that to the inner side of the great toe are derived from the ending of the dorsal 

 artery of the foot. 



Thus, as in the fingers, collateral digital arteries pass along the sides of the flexor 

 aspect of each of the toes, and then inosculate across the last phalanx so as to form 

 an arch, from the convexity of which minute vessels pass forwards to the extremity 

 of the toe, and upwards to the matrix of the nail. 



Anterior perforating branches, one in each space, are sent upwards by the digital 

 arteries near their bifurcation, to communicate with the interosseous arteries on the 

 dorsum of the foot. These branches are, however, often wanting in one or more of 

 the outer spaces. 



Varieties. The arteries of the foot deviate from the normal arrangement much less 

 frequently than those of the hand. 



The internal plantar artery is sometimes smaller than usual, and has been seen termina- 

 ting in the flexor brevis hallucis (Cruveilhier). On the other hand, it may be larger and 

 supply alone the digital artery of the inner side of the great toe, or even the arteries of the 

 contiguous sides of the great and second toes. 



The external plantar arttry occasionally varies in size, a diminution being accompanied 

 by an enlargement of the dorsal artery of the foot, and vice versa. It has been observed very 

 small, and not entering into the plantar arch, which was formed by the dorsal artery alone 

 (Dubrueil, Cruveilhier). 



The posterior perforating branches, which are usually very small vessels, are sometimes 

 enlarged, and furnish the interosseous arteries on the back of the foot, the metatarsal branch 

 of the dorsal artery, from which the dorsal interosseous arteries are usually derived, being in 

 that case very small. 



ANTERIOR TIBIAL ARTERY (IV). 



The anterior tibial artery, the smaller of the two divisions of the popliteal trunk, 

 extends from the lower border of the popliteus muscle to the bend of the ankle, 



