PLANTARIS SOLEUS. 



255 



die longest. They unite to form the beautiful muscle so Fig. 133 * 



characteristic of this region of the limb. It is inserted, 



by means of the tendo Achillis, into the lower part of 



the posterior tuberosity of the os calcis, a synovial bursa 



being placed between that tendon and the upper part of 



the tuberosity. The gastrocnemius must be removed 



from its origin, and turned down, in order to expose the 



next muscle. 



Relations. By its superficial surface, with the deep 

 fascia of the leg, which separates it from the external 

 saphenous vein, and with the external saphenous nerve. 

 By its deep surface, with the lateral portions of the pos- 

 terior ligament of the knee joint, the popliteus, plantaris, 

 and soleus. The internal head of the muscle rests 

 against the posterior surface of the internal condyle of 

 the femur ; the external head against the outer side of 

 the external condyle. In the latter, a sesamoid bone is 

 sometimes found. 



The PLANTARIS (planta, the sole of the foot), an ex- 

 tremely diminutive muscle, situated between the gastroc- 

 nemius and soleus, arises from the outer condyle of 

 the femur ; ' and is inserted, by its long and delicately 

 slender tendon, into the inner side of the posterior 

 tuberosity of the os calcis, by the side of the tendo 

 Achillis: having crossed obliquely between the two 

 muscles. 



The SOLEUS (solea, a sole), is the broad muscle upon 

 which the plantaris rests. It arises, from the head and 

 upper third of the fibula, from the oblique line and middle third of the 

 tibia. Its fibres converge to the tendo Achillis, by which it is inserted into 

 the posterior tuberosity of the os calcis. Between the fibular and tibial 

 origins of this muscle is a tendinous arch, beneath which the popliteal 

 vessels and nerve pass into the leg. 



Relations. By its superficial surface, with the gastrocnemius and plan- 

 taris. By its deep surface, w y ith the intermuscular fascia, which separates 

 it from the flexor longus digitorum, tibialis posticus, flexor longus pollicis, 

 from the posterior tibial vessels and nerve, and from the peroneal vessels. 



Actions. The three muscles of the calf draw powerfully on the os cal- 

 cis, and lift the heel ; continuing their action, they raise the. entire body. 

 This action is attained by means of a lever of the second power, the ful- 

 crum (the toes) being at one end, the weight (the body supported on the 

 tibia) in the middle, and the power (these muscles) at the other extremity. 



They are, therefore, the walking muscles, and perform all movements 

 that require the support of the whole body from the ground, as dancing, 

 leaping, &c. Taking their fixed point from below, they steady the leg 

 upon the foot. 



* The superficial muscles of the posterior aspect of the leg. 1. The biceps muscle 

 forming the outer hamstring. 2. The tendons forming the inner hamstring. 3. Th 

 popliteal space. 4. The gastrocnemius muscle. 5, 5. The soleus. 6. The tendo Achillis 

 7. The posterior tuberosity of the "os' calcis. 8. The tendons of the peroneus longus and 

 brevis muscles passing behind the outer ankle. 9. The tendons of the tibialis posticus 

 and llexor longus digitorum passing into the foot behind the inner ankle. 



