610 DISSECTION OF THE LEG. 



on the sides ; and it will not fully appear until after the membrane cover- 

 ing it has been divided longitudinally, and reflected to the sides. 



To prepare the peroneal artery, evert and partly divide the flexor pollicis 

 in which it is contained ; then follow branches of it to the fore part of the 

 leg, the outer side of the foot, and to join the posterior tibial artery. 



DEEP LAYER OF MUSCLES (fig. 209). The deep muscles at the back 

 of the leg are four in number, viz., popliteus, flexor longus pollicis, flexor 

 longus digitorum, and tibialis posticus. The first of these is close to the 

 knee-joint ; it crosses the bones, and is covered by a special aponeurosis 

 The flexors lie on the bones, the one of the great toe resting on the fibula, 

 and that of the other toes on the tibia. And the tibialis covers the inter- 

 osseous membrane. With the exception of the popliteus, all enter the 

 sole of the foot, and have a fleshy part parallel to the bones of the leg, and 

 a tendinous part beneath the tarsus. 



The POPLITEUS (fig. 209 A ) arises by tendon, within the capsule of the 

 knee-joint, from the fore part of an oblong depression on the outer surface 

 of the external condyle of the femur ; and external to the capsule of the 

 joint, some fleshy fibres arise from the posterior ligament. The tendon 

 gives rise to fibres, which are inserted into the tibia above the oblique line 

 on the posterior surface. 



The muscle rests on the tibia, and is covered by a fascia derived in great 

 part from the tendon of the semimembranosus muscle : on it lie the pop- 

 liteal vessels and nerve, and the gastrocnemius and plantaris. Along the 

 upper border are the lower articular vessels and nerve of the inner side of 

 the knee ; and the lower border corresponds with the attachment of the 

 soleus on the tibia. The origin will be seen with the dissection of the 

 ligaments of the knee-joint. 



Action. The leg being free, the muscle bends the knee-joint, and then 

 rotates inwards the tibia. The foot resting on the ground, it will support 

 the knee. According^ to the view of Theile, it retracts the external semi- 

 lunar fibro-cartilage. 



The FLEXOR LONGUS POLLICIS (fig. 209, F ) arises below the soleus from 

 the lower half or two thirds of the posterior surface of the fibula ; from 

 the intermuscular septum between it and the peronei muscles ; and from 

 the aponeurosis over the tibialis. Inferiorly the tendon of the muscle 

 enters a groove in the astragalus, and crosses the sole of the foot to its in- 

 sertion into the great toe. 



In part the muscle is covered by the soleus ; but in part it is superficial, 

 and is in contact with the fascia. It lies on the fibula and lower end of 

 the tibia, and conceals the peroneal vessels. Along the inner side are the 

 posterior tibial nerve and vessels : and contiguous to the outer margin, but 

 separated by fascia, are the peronei muscles. 



Action. The foot being unsupported, the flexor bends the last phalanx 

 of the great toe, and extends then the ankle. 



The foot resting on the ground, the muscle raises the heel ; and it moves 

 back the fibula as the body rises from stooping. 



The FLEXOR LONGUS DIGITORUM (fig. 209, E ) (flexor perforans) arises 

 from the posterior surface of the tibia, extending from the attachment of 

 the soleus to about three inches from the lower extremity ; and from the 

 aponeurosis covering the tibialis posticus. Its tendon enters a partition in 

 the annular ligament, which is superficial to the sheath of the tibialis ; and 

 it divides in the sole of the foot into tendons for the four outer toes. 



The muscle is narrow and pointed above, and is placed beneath the 



