524 THE MUSCLES AND FASCIA. 



bursa being interposed between the tendon and the upper part of this surface. The 

 tendon spreads out somewhat at its lower end, so that its narrowest part is usually 

 about an inch and a half above its insertion. The tendon is covered by the fascia 

 and the integument, and is separated from the deep muscles and vessels by a 

 considerable interval filled up with areolar and adipose tissue. Along its outer 

 side, but superficial to it, is the external saphenous vein. 



The Plantaris is an extremely diminutive muscle placed between the Gastro- 

 cnemius and Soleus, and remarkable for its long and delicate tendon. It arises 

 from the lower part of the outer prolongation of the linea aspera and from the 

 posterior ligament of the knee-joint. It forms a small fusiform belly, about three 

 or four inches in length, terminating in a long slender tendon which crosses 

 obliquely between the two muscles of the calf, and, running along the inner border 

 of the tendo Achillis, is inserted with it into the posterior part of the os calcis. 

 This muscle is occasionally double, and is sometimes wanting. Occasionally, its 

 tendon is lost in the internal annular ligament or in the fascia of the leg. 



Nerves. These muscles are supplied by the internal popliteal nerve, the Soleus 

 receiving an additional branch from the posterior tibial nerve. 



Actions. The muscles of the calf are constantly called into use in standing, 

 walking, dancing, and leaping. In walking these muscles draw powerfully upon 

 the os calcis, raising the heel, and with it the entire body, from the ground ; the 

 body being thus supported on the raised foot, the opposite limb can be carried 

 forward. In standing, the Soleus, taking its fixed point from below, steadies the 

 leg upon the foot, and prevents the body from falling forward, to which there is a 

 constant tendency from the superincumbent weight. The Gastrocnemius, acting 

 from below, serves to flex the femur upon the tibia, assisted by the Popliteus. The 

 Plantaris is the rudiment of a large muscle which exists in some of the lower 

 animals and serves as a tensor of the plantar fascia. In man it is merely an 

 accessory to the Gastrocnemius, extending the ankle if the foot is free or bending 

 the knee if the foot is fixed. 



Deep Layer. 



Popliteus. Flexor longus digitorum. 



Flexor longus hallucis. Tibialis posticus. 



Dissection. Detach the Soleus from its attachment to the fibula and tibia, and turn it 

 downward, when the deep layer of muscles is exposed, covered by the deep transverse fascia of 

 the leg. 



The Deep Transverse Fascia of the leg is a broad, transverse, intermuscular 

 septum interposed between the superficial and deep muscles in the posterior 

 tibio-fibular region. On either side it is connected to the margins of the tibia and 

 fibula. Above, where it covers the Popliteus, it is thick and dense, and receives an 

 expansion from the tendon of the Semimembranosus ; it is thinner in the middle 

 of the leg, but below, where it covers the tendons passing behind the malleoli, it 

 is thickened. It is continued onward in the interval between the ankle and the 

 heel, where it covers the vessels and is blended with the internal annular 

 ligament. 



This fascia should now be removed, commencing from below opposite the tendons, and 

 detaching it from the muscles in the direction of their fibres. 



The Popliteus is a thin, flat, triangular muscle, which forms part of the floor 

 of the popliteal space, and is covered by a tendinous expansion derived from the 

 Semimembranosus muscle. It arises by a strong tendon, about an inch in length, 

 from a deep depression on the outer side of the external condyle of the femur, 

 and from the posterior ligament of the knee-joint, and is inserted into the inner 

 two-thirds of the triangular surface above the oblique line on the posterior surface 

 of the shaft of the tibia, and into the tendinous expansion covering the surface 

 of the muscle. The tendon of the muscle is covered by that of the Biceps and the 

 external lateral ligament of the knee-joint; it grooves the outer border of the 



