480 MYOLOGY 



Nerves. The muscles of this region are supplied by the fourth and fifth lumbar and the first, 

 second, and third sacral nerves; the nerve to the short head of the Biceps femoris is derived froaa 

 the common peroneal, the other muscles are supplied through the tibial nerve. 



Actions. The hamstring muscles flex the leg upon the thigh. When the knee is semiflexed, 

 the Biceps femoris in consequence of its oblique direction rotates the leg slightly outward; and 

 the Semitendinosus, and to a slight extent the Semimembranosus, rotate the leg inward, assist- 

 ing the Popliteus. Taking their fixed point from below, these muscles serve to support the pelvis 

 upon the head of the femur, and to draw the trunk directly backward, as in raising it from the 

 stooping position or in feats of strength, when the body is thrown backward in the form of an 

 arch. As already indicated on page 285, complete flexion of the hip cannot be effected unless 

 the knee-joint is also flexed, on account of the shortness of the hamstring muscles. 



m. THE MUSCLES AND FASCLE OF THE LEG. 



The muscles of the leg may be divided into three groups: anterior, posterior, 

 and lateral. 



1. The Anterior Crural Muscles (Fig. 437). 



Tibialis anterior. Extensor digitorum longus. 



Extensor hallucis longus. Peronseus tertius. 



Deep Fascia (fascia cruris) . The deep fascia of the leg forms a complete invest- 

 ment to the muscles, and is fused with the periosteum over the subcutaneous 

 surfaces of the bones. It is continuous above with the fascia lata, and is attached 

 around the knee to the patella, the ligamentum patellae, the tuberosity and con- 

 dyles of the tibia, and the head of the fibula. Behind, it forms the popliteal fascia, 

 covering in the popliteal fossa; here it is strengthened by transverse fibers, and 

 perforated by the small saphenous vein. It receives an expansion from the tendon 

 of the Biceps femoris laterally, and from the tendons of the Sartorius, Gracilis, 

 Semitendinosus, and Semimembranosus medially; in front, it blends with the peri- 

 osteum covering the subcutaneous surface of the tibia, and with that covering 

 the head and malleolus of the fibula; below, it is continuous with the transverse 

 crural and laciniate ligaments. It is thick and dense in the upper and anterior 

 part of the leg, and gives attachment, by its deep surface, to the Tibialis anterior 

 and Extensor digitorum longus; but thinner behind, where it covers the Gastroc- 

 nemius and Soleus. It gives off from its deep surface, on the lateral side of the leg, 

 two strong intermuscular septa, the anterior and posterior peroneal septa, which 

 enclose the Peronsei longus and brevis, and separate them from the muscles of 

 the anterior and posterior crural regions, and several more slender processes which 

 enclose the individual muscles in each region. A broad transverse intermuscular 

 septum, called the deep transverse fascia of the leg, intervenes between the super- 

 ficial and deep posterior crural muscles. 



The Tibialis anterior (Tibialis anticus) is situated on the lateral side of the tibia; 

 it is thick and fleshy above, tendinous below. It arises from the lateral condyle 

 and upper half or two-thirds of the lateral surface of the body of the tibia; from 

 the adjoining part of the interosseous membrane; from the deep surface of the 

 fascia; and from the intermuscular septum between it and the Extensor digitorum 

 longus. The fibers run vertically downward, and end in a tendon, which is apparent 

 on the anterior surface of the muscle at the lower third of the leg. After passing 

 through the most medial compartments of the transverse and cruciate crural 

 ligaments, it is inserted into the medial and under surface of the first cuneiform 

 bone, and the base of the first metatarsal bone. This muscle overlaps the anterior 

 tibial vessels and deep peroneal nerve in the upper part of the leg. 



Variations. A deep portion of the muscle is rarely inserted into the talus, or a tendinous slip 

 may pass to the head of the first metatarsal bone or the base of the first phalanx of the great toe. 

 The Tibiofasdalis anterior, a small muscle from the lower part of the tibia to the transverse or 

 cruciate crural ligaments or deep fascia. 



