2o6 THE MUSCLES. 



of the fibula, and by tendon-fibres from the proximal two-fifths 

 of its ventral border. 



Insertion. — The muscle ends in a slender tendon which 

 joins the lateral border of the gastrocnemius tendon to form the 

 tendon of Achilles (Fig. 90, /), which forms the sheath of the 

 plantaris tendon. 



Relations. — Outer surface with the gastrocnemius (Fig. 90, 

 VI) and plantaris (Fig. 90, /). Inner surface with the peroneus 

 longus (Fig. 90, q), peroneus tertius (Fig. 90, r), and flexor 

 hallucis (Fig. 91, vi). 



Action. — Assists the gastrocnemius to extend the foot. 



M. triceps surae. — The gastrocnemius and the soleus are 

 sometimes considered as forming a single muscle, with three 

 heads, under the name triceps surae. 



M. popliteus (Fig. 92, k). — A triangular muscle passing 

 from the femur obliquely toward the medial side over the ven- 

 tral surface of the proximal end of the tibia. 



Origin by a strong tendon from the popliteal groove on the 

 surface of the lateral epicondyle of the femur. In the tendon 

 is a sesamoid bone, the popliteal bone (Fig. 61, 5, page 89), 

 which glides over the ventral part of the lateral articular facet 

 on the proximal end of the tibia. As the muscle passes over 

 the joint it is closely attached to the joint capsule. From the 

 popliteal bone, which with the tendon lies within the capsule 

 of the knee-joint, the muscle-fibres diverge to their 



Insertion into the proximal end of the ventral surface of the 

 tibial shaft on the medial side of the medial oblique ridge. 

 The area of insertion extends slightly onto the medial surface 

 of the bone. 



Relations. — Outer surface with the gastrocnemius (Fig. 

 92,7) and plantaris (Fig. 91, /), and with the tendon of the 

 semitendinosus (Fig. 92, /). Distal border with the origins 

 of the soleus and flexor longus digitorum. Inner surface with 

 the capsule of the knee-joint and the tibia. 



Action. — Rotates the thigh so as to turn the toes inward. 



The three following deep muscles on the ventral surface of 

 the shank are covered by a deep fascia (the deep crural fascia) 



