246 ANATOMY OF THE LOWER EXTREMITY. 



The sheaths of the flexor tendons consist of transverse 

 fibrous bands which hold the tendons down upon the 

 phalanges; though similar to those of the fingers, they are 

 not so distinct nor so well developed. 



The ABDUCTOR POLLICIS PEDIS lies upon the side of the 

 great toe ; it arises by two heads, which are not, however, 

 well-marked divisions ; one springs from the internal annular 

 ligament which covers in the vessels and tendons below 

 the inner malleolus, the other from the inner tuberosity of 

 the os calcis. Between these heads pass the plantar ves- 

 sels, nerves, and tendons. It is inserted, after uniting with 

 the tendon of the flexor breyis pollicis, into the base of the 

 first phalanx of the great toe. 



The ABDUCTOR MINIMI DIGITI PEDIS is placed along the 

 outer edge of the foot ; it arises from the external surface 

 of the os calcis, and from the plantar fascia which covers 

 it, and is inserted into the base of the first phalanx of the 

 little toe. 



The flexor brevis digitorum is separated from the mus- 

 cles on each side of it by strong intermuscular septa ; the 

 inner of these is perforated by the internal plantar nerve 

 and by the tendon of the flexor longus pollicis ; the outer 

 by a nerve and artery destined to the little toe. 



The flexor brevis digitorum and abductor minimi digiti should be 

 divided, and their two ends reflected ; the tendons of the long flexor, 

 with the plantar vessels and nerves, will then be exposed, and should 

 be cleared from the superfluous areolar tissue which invests them. 



The posterior tibial artery, on entering the sole of the 

 foot, divides into the internal and external plantar arteries. 



The internal plantar artery passes between the abductor pollicis and 

 flexor brevis digitorum to the great toe ; it gives off small muscular 

 branches, and terminates in supplying the sides of the great toe ; 

 it anastomoses with the digital branches of the external plantar artery, 

 and the communicating branch of the dorsalis pedis. 



The external plantar artery is larger than the internal ; it passes 

 obliquely beneath the flexor brevis digitorum to the base of the fifth 

 metatarsal bone, and then curves transversely across the foot, dipping 

 beneath the deeper muscles, to the first interosseous space, which it 

 penetrates to anastomose with the dorsalis pedis artery. 



The nerves of the sole of the foot are derived from the 

 posterior tibial nerve, which, at the inner malleolus, divides 

 into external and internal plantar branches. 



