FASCIA AND MUSCLES OF THE SOLE OF THE FOOT Zll 



Nerve-supply. — From the postcriin' tilnal, which sends hranches forwards to 

 the l)aek of the muscle in the U])i)er third of the leg. 



Action. — (I) To adduct the front of the foot; (2) to invert the sole; (3) to 

 extend the ankle — the last of these movements is somewhat limited; (4) to siipijort 

 the longitudinal arch of the foot — first, by drawing backwards the lower part of 

 the scaphoid, and so preventing the descent of tlie head of the astragalus between 

 the scaphoid and calcaneum, and secondly by its traction upon the other tarsal 

 bones into which the secondary offsets of its tendon are inserted. 



Relations. — Superficially, the soleus and third layer of muscles of the leg, the 

 l)osterior tibial and peroneal vessels and the posterior tibial nerve above; in the 

 sole the tendon of the flexor longus digitorum and the abductor hallucis; deeply, 

 the ankle-joint and inferior caleaneo-scaphoid ligament. The anterior tibial vessels 

 pass through a notch at the upper extremity of the muscle, Ijetween its tiliial and 

 fibular origins. 



THE FASCIA AND MUSCLES OF THE SOLE 

 OF THE FOOT 



The plantar fascia is, like the corresponding fascia in the palm, very strong, 

 and is divided into three parts. The central part, which is the strongest, arises 

 from the under surface of the calcaneum at the back of the tubercles. It is 

 triangular, the apex being attached behind, and the expanded base dividing 

 near the heads of the metatarsal bones into five divisions, one for each of the toes. 

 Each division forms an arch over the tendons entering the toe, and is continuous 

 with the ligamentum vaginale of the theca. The sides of the arch pass upwards to 

 hit attached to the deep transverse ligament which connects the heads of the meta- 

 tarsal bones, and to the lateral ligaments of the metatarso-phalangeal joints. The 

 under surface of the fascia is attached to the deep surface of the skin by small 

 fil)rous bands which form the walls of compartments containing pellets of fat. 

 These fibrous connections give firmness to the skin of the sole and prevent it from 

 being moved about upon the subjacent fascia. The borders of the central portion 

 of the plantar fascia are continued upwards into the sole by the internal and external 

 inter mil scidar septa, which are attached above to the fibrous structures on the under 

 surfaces of the tarsal bones. The inner portion, which is the thinnest division of 

 the plantar fascia, is attached behind to the inner Itorder of the great tubercle of the 

 calcaneum and to the lower border of the internal annular ligament. It is inserted 

 in front upon the inner side of the base of the first phalanx of the great toe, and 

 above it becomes continuous wdth the deep fascia covering the instep. The ex- 

 ternal portion is very thick, and arises from the outer border of the lesser tul)ercle 

 of tlie calcaneum and the lower border of the external annular ligament. It ter- 

 minates in front in the base of the first phalanx of the little toe, and at its inner 

 border it blends with the central portion of the plantar fascia, Avhere it is joined by 

 the external intermuscular septum; ujwn its outer border it is closely connected 

 with the l)ase of the fifth metatarsal bone, and it is continuous with the deep fascia 

 covering the instep. 



In tlie web between the toes some thin transverse fibres are found, the super- 

 ficial transverse ligament of the toes. They bridge over part of the interval 

 between the live sli}>s into which the front part of the central division of the 

 l)lantar fascia breaks up. 



The muscles and tendons in the sole of the foot are divided into four layers. 

 The first layer consists of three muscles, which corresi)ond in their position to the 

 three compartments formed l)y the ])lantar fascia and the two intennuscular septa, 

 viz. the abductor hallucis, the fiexor brevis digitorum, the abductor minimi digiti. 



