612 DISSECTION OF THE LEG. 



as far down as the lowest fifth. In the lower part of the leg the muscle is 

 directed beneath the flexor digitorum ; and its tendon, entering the inner 

 space in the annular ligament, reaches the inner side of the foot to be in- 

 serted into the scaphoid and other bones (p. 625). 



The tibialis is concealed by the aponeurosis before mentioned, and is 

 overlapped by the neighboring muscles ; but in the lower part of the leg it 

 is placed between the tibia and the long flexor of the toes. On the mus- 

 cle are the posterior tibial vessels and nerve. The upper part presents two 

 pointed processes of attachment that to the tibia being the highest be- 

 tween which the anterior tibial vessels are directed forwards. 



Action. Its action on the movable foot is to shorten the inner border by 

 drawing down the scaphoid bone, and to extend the ankle joint. The toes 

 resting on the ground, it will aid the muscles of the calf in raising the heel 

 in the progression of the body. 



In standing, the muscle can raise the inner border of the foot with the 

 tibialis anticus, so as to throw the weight of the body on the outer edge. 



As the body rises from stooping, the tibialis draws back the bones of 

 the leg, with the soleus. 



The aponeurosis covering the tibialis is attached laterally to the bones, 

 but has a defined border inferiorly over the muscle. By one surface it 

 gives origin to the flexors of the toes, and by the other to the tibialis. 



The POSTERIOR TIBIAL ARTERY (fig. 209, e) is one of the branches 

 resulting from the bifurcation of the popliteal trunk. The vessel extends 

 from the lower border of the popliteus muscle to the lower part of the 

 internal annular ligament, where it ends in two plantar branches for the 

 sole of the foot. 



At its origin the artery lies midway between the tibia and fibula, but as 

 it approaches the lower part of the leg it gradually inclines inwards; and 

 at its termination it is placed below the tibia, internal to the centre of the 

 hollow between the heel and the inner ankle. 



As far as the middle (in length) of the leg the vessel is concealed by 

 two muscles of the calf, viz., gastrocnemius and soleus ; but below that 

 spot, as it lies between the tendo Achillis and the inner edge of the tibia, 

 it is covered only by the teguments and the deep fascia. At its termina- 

 tion it is placed beneath the annular ligament. For its upper half the 

 trunk lies over the tibialis posticus, but afterwards on the flexor digitorum, 

 and on the lower end of the tibia and the ankle-joint. On the outer side 

 is the flexor pollicis. 



Between the heel and the ankle, the artery is placed between the ten- 

 dons of the common flexor of the digits and special flexor of the great toe. 



Venas comites closely surround the vessel. The posterior tibial nerve 

 is at first internal to the artery ; but at the distance of one inch and a half 

 it crosses to the outer side, and retains that position throughout. 



This artery supplies branches to the muscles and the tibia, and a large 

 peroneal trunk to the outer side of the leg. 



a. Muscular branches enter the deep layer of muscles, and the soleus ; 

 and an offset from the branch to the soleus pierces the attachment of that 

 muscle to the tibia, and ascends to the knee-joint. 



b. A nutritious artery of the shaft of the tibia is uncertain in its place 

 of origin ; penetrating the tibialis, it enters the canal on the posterior sur- 

 face of the bone, and ramifies in the interior. 



c. A communicating branch (/) arises opposite the lower end of the 



