THE MUSCLES OF THE FOOT. 



659 



Os calcis, inner tubercle 



Calcaneo-metatarsal 

 ligament 



Action. — To extend and evert the foot. 



Variations. — A slip is very frequently given off from the tendon of the short peroneus 

 which is inserted either into the tendon of the extensor longus digitorum passing to the fifth toe 

 or directly into that digit. In some cases the slip arises from the belly of the muscle, from that 

 of the peroneus longus, or even from the fibula directly, and represents what has been termed 

 the peroneus qiiintus. 



Aperojieus quartus, where distinctness from the quintus seems doubtful, sometimes occurs as 

 a muscle arising from the lower part of the fibula and inserting into the calcaneum or the tuber- 

 osity of the cuboid. 



THE MUSCLES OF THE FOOT. 



The plantar fascia or aponeurosis (Fig. 626) is a dense sheet of connective 

 tissue lying immediately beneath the skin of the plantar surface of the foot and 

 covering the pre-axial mus- 

 cles. It is attached behind ^^^- ^'^^• 

 to the tuberosity of the cal- 

 caneum, and extends dis- 

 tally in a fan-like manner to 

 be attached by five processes 

 to the skin over the meta- 

 tarso-phalangeal joints of 

 the digits. The aponeuro- 

 sis is much thicker in its 

 middle portion than at the 

 sides, where it is continued 

 dorsally over the sides of 

 the foot to become continu- 

 ous with the fascia of the dor- 

 sum of the foot and with the 

 crural fascia. Between its 

 cutaneous insertions trans- 

 verse bands of fibres stretch 

 across to form the super- 

 ficial transverse metatarsal 

 ligament (fasciculi trans- 

 versi) ; frOm its deep sur- 

 face strong sheets are given 

 of? which pass to the sheaths 

 of the flexor tendons. Ex- 

 pansions are also given off 

 from its deep surface which 

 invest the fiexor brevis digi- 

 torum and, on either side, 

 the abductor hallucis and 

 abductor minimi digiti. 



Between the aponeu- 

 rosis and the integument 

 over the inferior surface of 

 the tuberosity of the calca- 

 neum a bursa (bursa subcu- 

 tanea calc^nea) is constantly 

 present. 



The dorsal surface of 

 the foot is covered by the fascia dorsalis pedis, a rather thin sheet continuous with 

 the crural fascia above. It covers the long extensor tendons. 



Plantar fascia,' 

 central portion 



Plantar fascia, 

 inner lateral 

 portion 



Plantar fascia, 

 slip for great toe- 



Flexor longus- 

 hallucis tendon 



Superficial- 

 transverse met- 

 atarsal ligament 



Plantar fascia, 

 outer lateral 

 portion 



Plantar fascia 

 digital slips 



Superficial dissection of sole of right foot (subject lying 

 on belly), showing plantar fascia. 



(a). THE PRE-AXIAL MUSCLES. 



Like the pre-axial muscles of the hand, those of the foot may be regarded as 

 derived from five' primary layers, which have undergone a considerable amount of 

 modification, including some fusion. 



