478 POSTERIOR TIBIAL NERVE. 



and sending numerous filaments to the integument of the heel and 

 sole of the foot. 



The POSTERIOR TIBIAL NERVE is continued along the posterior 

 aspect of the leg from the lower border of the popliteus muscle to the 

 posterior part of the inner ankle, where it divides into the internal 

 and external plantar nerve. In the upper part of its course it lies 

 to the outer side of the posterior tibial artery ; it then becomes 

 placed superficially to that vessel, and at the ankle is again situated 

 to its outer side ; in the lower third of the leg it lies parallel with the 

 inner border of the tendo Achillis. 



The Brandies of the posterior tibial nerve are three or four muscular 

 twigs to the deep muscles of the posterior aspect of the leg, the 

 branch to the flexor longus pollicis accompanies the fibular artery ; 

 one or two filaments which entwine around the artery and then ter- 

 minate in the integument;* and two or three plantar cutaneous 

 branches which pass downwards upon the inner side of the os calcis 

 and are distributed to the integument of the heel. 



The INTERNAL PLANTAR NERVE, larger than the external, crosses 

 the posterior tibial vessels to enter the sole of the foot, where it lies 

 in the interspace between the abductor pollicis and flexor brevis digi- 

 torum ; it then enters the sheath of the latter muscle, and divides op- 

 posite the bases of the metatarsal bones into three digital branches ; 

 one to supply the adjoining sides of the great and second toe ; the se- 

 cond the adjoining sides of the second and third toe ; and the third 

 the corresponding sides of the third and fourth toes. This distribution 

 is precisely similar to that of the digital branches of the median 

 nerve. 



In its course the internal plantar nerve gives off cutaneous branches 

 to the integument of the inner side and sole of the foot ; muscular 

 branches to the muscles forming the inner and middle group of the 

 sole ; a digital branch to the inner border of the great toe ; and arti- 

 cular branches to the articulations of the tarsal and metatarsal bones. 



The EXTERNAL PLANTAR NERVE, the smaller of the two, follows 

 the course of the external plantar artery to the outer border of the 

 musculus accessorius, beneath which it sends several large muscular 

 branches to supply the adductor pollicis and the articulations of the 

 tarsal and metatarsal bones. It then gives branches to the integu- 

 ment of the outer border and sole of the foot, and sends forward two 

 digital branches to supply the little toe and one half the next. 



* It is extremely interesting in a physiological point of view, to observe the 

 mode of distribution of these filaments. I have traced them in relation with 

 several, and I have no doubt that they exist in connection with all the superfi- 

 cial arteries. They seem to be the direct monitors to the artery of the presence 

 or approach of danger. 



