POSTERIOR TIBIAL ARTERY. 195 



constituting a fibular origin of that muscle. Fibres of the flexor 

 longus hallueis arise from one surface of the membrane, and of the 

 tibialis posticus from the other. 



The POSTERIOR TIBIAL ARTERY (fig. 74, e) is one of the vessels Posterior 

 ivsulting from the bifurcation of the popliteal trunk (p. 126). It artery: 

 extends from the lower border of the popliteus muscle to the lower extent; 

 edge of the internal annular ligament, where it ends in internal and 

 f:i-tfnt<il plantar branches for the sole of the foot. 



At its origin the artery lies midway between the tibia and fibula course; 

 but as it approaches the lower part of the leg it gradually inclines 

 inwards ; and at its termination it is placed behind the tibia, in the 

 centre of the hollow between the heel and the inner ankle. 



For the upper two-thirds of the leg the vessel is concealed by two parts cover- 

 muscles of the calf, viz., gastrocnemius and soleus ; but in the aiVbeiowf 

 lower third, as it lies between the tendo Achillis and the inner 

 edge of the tibia, it is covered only by the integuments and the 

 deep fascia. At its termination 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 parts be- 

 end of the tibia and the ankle-joint. On the outer side is the neathlt; 

 flexor hallueis. 



Under the annular ligament, the artery is placed between the between 

 tendons of the common flexor of the digits and the special flexor of 

 the great toe. 



Yen 8e comites closely surround the vessel. The posterior tibial veins; 

 nerve is at first internal to the artery ; but after the origin of the nerve ; 

 peroneal artery it crosses to the outer side, and retains that position 

 throughout. 



This artery supplies BRANCHES to the muscles and the tibia, and a branches : 

 large PEROXEAL trunk to the outer side of the leg. 



K. J/^*n</Vn' branches enter the deep layer of muscles, and the Muscular, 

 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. The medullary artery of the tibia arises near the beginning of Medullary 

 the trunk ; penetrating the tibialis, it enters the canal on the posterior 

 surface of the bone, and ramifies in the interior. 



c. Cutaneous offsets appear through the fascia in the lower half Cutaneous, 

 of the leg. 



d. One or two small internal maUmlar branches ramify over the internal 

 inner malleolus. 



e. A communicating branch arises opposite the lower end of the Communi- 

 tibia, and passes outwards beneath the flexor longus hallueis, to ca 

 unite in an arch with a corresponding offset of the peroneal artery. 

 Sometimes there is a second loop between these vessels superficial to 



the flexor hallueis (fig. 74, /). 



Peculiarities. If the posterior tibial artery is smaller than usual, or size of 

 absent, its deficiencies in the foot will be supplied by a large communicating tibial may 

 branch from the peroneal artery, which, in these cases, is directed inwards vary - 

 at the lower end of the tibia, and either joins the small tibial vessel, or runs 

 alone to the sole of the foot. 



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