454 THE MUSCULATURE 



arises from the two epicondyles of the femur, and the soleus which arises from the 

 tibia and fibula. These powerful extensors of the ankle are inserted by means of 

 the tendon of Achilles into the calcaneus. The gastrocnemius is a flexor of the 

 knee as well as an extensor of the ankle. A rudimentary muscle, the plantaris, 

 arises near the lateral head of the gastrocnemius and is inserted into the fibrous 

 tissue of the heel. 



The deep group ffig. 416) consists of one muscle, the popliteus, a medial 

 rotator and flexor of the leg, which arises from the lateral condyle of the femur and 

 is inserted into the tibia; and of three muscles, the flexor digitorum long^is, flexor 

 hallucis longus and tibialis posterior, which arise from the tibia and fibula, send 

 tendons behind the medial malleolus and are inserted into the plantar surface of 

 the tarsus and into the terminal phalanges of the toes. They invert the foot and 

 flex the toes. 



In the foot one muscle on the dorsum represents the primitive dorsal division, 

 the extensor digitorum brevis (fig. 418), supplied by a branch from the peroneal 

 nerve. On the other hand the primitive ventral division is well represented in 

 the sole of the foot, not only by the muscles associated with the long flexor tendons, 

 quadratus plantse, lumbricales (flg. 420), but also by the short flexor of the toes 

 (fig. 419), b}^ the special musculature of the big and little toes (fig. 421) and by the 

 interosseous muscles (fig. 422). The flexor digitorum brevis (fig. 419), the most 

 superficial of these muscles, arises from the calcaneus and is inserted into the 

 second row of phalanges of the four more lateral toes. The quadratus plantce 

 arises from the calcaneus and is inserted into the tendon of the long extensor of 

 the toes. It makes the action of the tendon on the digits more direct. The four 

 lumbrical muscles run from this tendon to the medial sides of the four lateral toes. 

 They flex the digits. Of the intrinsic muscles of the great toe (figs. 419, 421), 

 the abductor arises from the calcaneus; the flexor brevis from the cuneiform 

 bones; and the adductor, by one head from the long plantar ligament, by the other 

 from the capsules of the metatarso-phalangeal joints. All are inserted into the 

 base of the first phalanx. Of the muscles of the little toe (figs. 419-421), the abduc- 

 tor arises from the calcaneus, the flexor and opponens from the cuboid. The two 

 former are attached to the base of the first phalanx, the last to the fifth metatarsal. 

 The interosseous muscles which arise between the metatarsals are so arranged 

 that the three plantar abduct and the four dorsal adduct the four lateral toes to 

 and from an axis passing through the second toe. The muscles of the sole of the 

 foot which send tendons to the sides of the bases of the first row of phalanges help 

 to flex the digits on the metatarsals and to extend the toes at the first row of inter- 

 phalangeal joints. These are much less effective extensors of the phalanges than 

 are the corresponding muscles of the hand and, unlike the latter, seem, in most 

 individuals, to exert but little extensor action on the third row of phalanges. 

 The muscles of the sole of the foot are supplied by the lateral and medial plantar 

 branches of the tibial nerve. 



The muscle fasciae of the inferior extremity are well developed. The fascia lata, which 

 •em;loses the niusfulature of the back of the hip and the musculature of the thigh, is especially 

 .strong on the lateral side where it includes the longitudinal bundles of fibres which compose 

 the ilio-tibial band. From the fascia lata strong intermuscular septa extend on each side of the 

 quadriceps group of muscles to the femur. Medially beneath the sartorius muscle (fig. 410), 

 septa help to bound Hunter's canal in which lies the femoral artery on its way to the popliteal 

 space behind the knee. In the leg there is likewise a strong cylindrical fascial sheath which 

 encloses the musculature and sends septa on each side of the peroneal group to the fibula. A 

 transverse septum also separates the deep from the suj)erficial muscles of the calf. The fascia 

 of the leg is especially well developed near the ankle where it helps to hold in place the tendons 

 which pass from the muscles of the leg into the foot. Muscle fascite are well developed both on 

 the dorsum and in the sole of the foot. 



A. MUSCULATURE OF THE HIP 



1. Ilio-Femoral Musculature 



Tlu! iliac biudc; divides tiicsc muscles into an anterior group (ilio-psoas), 

 supplied by nerves from the lumbar plexus, and a posterior group (the gluteal 

 muscles, piriformis, and tensor fasciae lata?, supplied by nerves from the sacral 

 plexus. 



