MUSCLES OF LEG 477 



C. MUSCULATURE OF THE LEG 



(Figs. 413-422) 



The musculature of the leg arises in part from the distal end of the femur, 

 but in the main from the tibia and fibula. The muscle-bellies are best developed 

 in the proximal half of the leg, where they give rise to the ' calf behind and to less 

 well-marked ventral and lateral protrusions. Toward the ankle the muscle- 

 bellies give way to tendons which attach the muscles of the leg to the skeleton of 

 the foot. 



The musculature is divisible into an anterior, a lateral and a posterior group of 

 muscles. The anterior and lateral groups are separated from one another by an 

 intermuscular septum. The antero-lateral groups are separated from the pos- 

 terior group by the tibia and fibula, the interosseous membrane, and by an 

 intermuscular septum which extends from the lateral margin of the shaft of the 

 fibula to the fascia enveloping the leg. Medially the separation is well marked 

 by the broad medial surface of the tibia. Lateral!}' the line of division is not so 

 clearly marked externally. In the proximal part of the leg the dorsal musculature 

 protrudes somewhat ventrally; in the distal part the lateral musculature passes 

 dorsal to the lower end of the fibula. The posterior group is divided by a trans- 

 verse septum into superficial and deep divisions. 



While in the forearm the extensor-supinator muscles extend proximally on the radial side 

 of the arm to the humerus, and the flexor-pronator muscles on the ulnar side, in the leg both 

 of the corresponding sets of muscles extend primitively on the fibular side of the leg to the femur. 

 In the higher vertebrates the superficial layer of the flexor musculature of the leg takes origin 

 from both sides of the distal extremity of the femur, and the origin of the extensor musculatm^e 

 ceases to extend to the femur. The crural musculature is primitively inserted into the bones of 

 the leg, the tarsus, and the aponeuroses of the foot. On the extensor side of the leg the muscula- 

 ture ultimately becomes attached wholly to the foot by means of tendons differentiated, in part 

 at least, from the dorsal aponeurosis. The lateral portion of the extensor musculature, which 

 primitively extends from the femur to the fibula, in the higher vertebrates extends from the 

 fibula to the tarsus and metatarsus (peroneal musculature). On the flexor side of the leg the 

 more superficial musculature maintains a tarsal attachment through the tendon of Achilles. 

 The deeper musculature in part extends from the femur and fibula to the tibia, in part arises 

 from the fibula and tibia, and is inserted into the metatarsus and the digits through tendons 

 differentiated from the plantar aponeuroses. The musculature of the sole of the foot is highly 

 developed in five-toed vertebrates, but in those which walk on the toes, and especially in hoofed 

 animals, it is very greatly reduced. 



FASCIA OF THE LEG 



The tela subcutanea of the leg contains a considerable amount of fat w-here it overlies the 

 muscles, but less where it overlies the bones and joints. Subcutaneous bursae are found over 

 the tuberosity of the tibia (b. subcutanea tuberositatis tibiae) and over each of the malleoh 

 (b. subcutanea malleoli medialis et lateralis). Over the dorsum of the foot the tela contains 

 comparatively little fat, but on the sole of the foot and plantar surface of the toes it contains 

 much fat interposed between dense fibrous tissue. The b. subcutanea calcanea lies beneath 

 the tuber calcanei. 



The crural fascia, or external layer of fascia of the leg, extends from the knee to the ankle. 

 It forms an enveloping cone-Hke sheath for the muscles and is adherent to the periosteum of 

 the medial surface of the tibia. It is formed of transverse, oblique, and longitudinal fibres 

 and is thickest in front. 



Ventrally the fascia of the thigh, to which the tendons of the quadriceps, sartorius, gracilis, 

 semitendinosus, and biceps muscles and the ilio-tibial band are closely united, becomes attached 

 with these tendons to the tibia and fibula. From these attachments, therefore, the fascia of 

 the front of the leg may be said to arise. Into it extend processes from the tendons men- 

 tioned. Dorsally the fascia of the thigh is continued uninterruptedly into that of the leg. 

 Distally the crural fascia is attached to the two malleoli and to the posterior surface of the 

 calcaneus. 



In the proximal part of the leg in front the underlying muscles in part take origin from the 

 fascia; in other places the fascia is separated from the underlying muscles by loose tissue. 



From the fascia two main intermuscular septa arise. One, the anterior intermuscular 

 septum, extends between the extensor digitorum longus and peroneal muscles to the anterior 

 crest of the fibula; the other, the posterior intermuscular septum, between the peroneal muscles 

 and the soleus to the lateral crest of the fibula. These septa separate compartments for the 

 anterior, lateral, and posterior groups of muscles. 



As the heads of the gastrocnemius pass over the back of the knee they are held in place by a 

 special deep lamina of the fascia lata, which distally becomes fused with the crural fascia (fig. 

 414 A). 



