ANTERIOR TIBIAL REGION. 263 



ternal head of the gastrocnemius, the knee-joint from which it is 

 separated by a synovial membrane, and the popliteal artery and vein. 

 By its inner border with the gracilis. By its outer border with the 

 great ischiatic nerve, and in the popliteal space with the popliteal 

 artery and vein. 



If the semi-membranosus muscle be turned down from its origin, the 

 student will bring into view the broad and radiated expanse of the 

 adductor magnus, upon which the three flexor muscles above de- 

 scribed rest. 



Actions. These three hamstring muscles are the direct flexors of 

 the leg upon the thigh ; and, by taking their origin from below, they 

 balance the pelvis on the lower extremities. The biceps, from the 

 obliquity of its direction, everts the leg when partly flexed, and the 

 semi-tendinosus turns the leg inwards when in the same state of 

 flexion. 



Anterior Tibial Region. 



Tibialis anticus, 

 Extensor longus digitorum, 

 Peroneus tertius, 

 Extensor proprius pollicis. 



Dissection. The dissection of the anterior tibial region is to be 

 commenced by carrying an incision along the middle of the leg, mid- 

 way between the tibia and the fibula, from the knee to the ankle, and 

 bounding it inferiorly by a transverse incision extending from one 

 malleolus to the other. And to expose the tendons on the dorsum of 

 the foot, the longitudinal incision may be carried onwards to the outer 

 side of the base of the great toe, and be terminated by another incision 

 directed across the heads of the metatarsal bones. 



The TIBIALIS ANTICUS muscle (flexor tarsi tibialis) arises from the 

 upper two-thirds of the tibia, from the interosseous membrane, and 

 from the deep fascia ; its tendon passes through a distinct sheath 

 in the annular ligament, and is inserted into the inner side of the 

 internal cuneiform bone, and base of the metatarsal bone of the 

 great toe. 



Relations. By its anterior surface with the deep fascia, from which 

 many of its superior fibres arise, and with the anterior annular liga- 

 ment. By its posterior surface with the interosseous membrane, 

 tibia, ankle-joint, and bones of the tarsus with their articulations. By 

 its internal surface with the tibia. By the external surface with the 

 extensor longus digitorum, extensor proprius pollicis, and the anterior 

 tibial vessels and nerve. 



The EXTENSOR LONGUS DIGITORUM arises from the head of the 

 tibia, from the upper three-fourths of the fibula, from the interosseous 

 membrane, and from the deep fascia. Below, it divides into four ten- 

 dons, which pass beneath the annular ligament, to be inserted into the 

 second and third phalanges of the four lesser toes. The mode of in- 

 sertion of the extensor tendons, both in the hand and in the foot, is 



