POSTERIOR TIBIAL REGION. 



265 



Relations- By its anterior surface 

 with the deep fascia of the leg and Fi S- 10 7- 



foot, and with the anterior annular 

 ligament. By its posterior surface 

 with the interosseous membrane, the 

 fibula, the tibia, the ankle-joint, the 

 extensor brevis digitorum, and the 

 bones and articulations of the great 

 toe. It is crossed upon this aspect 

 by the anterior tibial vessels and nerve. 

 By its outer side with the extensor 

 longus digitorum, and in the foot with 

 the dorsalis pedis artery and veins ; 

 the outer side of its tendon upon the 

 dorsum of the foot being the guide to 

 these vessels. By its inner side with 

 the tibialis anticus, and with the ante- 

 rior tibial vessels. 



Actions. The tibialis anticus and 

 peroneus tertius are direct flexors of the 

 tarsus upon the leg ; acting in conjunc- 

 tion with the tibialis posticus they 

 direct the foot inwards, and with the 

 peroneus longus and brevis outwards. 

 They assist also in preserving the flat- 

 ness of the foot during progression. 

 The extensor longus digitorum and 

 extensor proprius pollicis, are direct 

 extensors of the phalanges; but, con- 

 tinuing their action, they assist the 

 tibialis anticus and peroneus tertius, in 

 flexing the entire foot upon the leg. 

 Taking their origin from below, they 

 increase the stability of the ankle-joint. 



Posterior Tibial Region. 

 Superficial Group. 

 Gastrocnemius, 

 Plantaris, 

 Soleus. 



Dissection. Make an incision from the middle of the popliteal 



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

 muscle, forming the outer hamstring. 2. The tendons forming the inner ham- 

 string. 3. The 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 flexor longus digito- 

 rum passing into the foot behind this inner ankle. 



