THE INTERNAL PLANTAR NERVE. 333 



Branches. The deep muscles on the back of the leg, the fibula, the integument 

 of the sole of the foot, and the ankle-joint receive branches from the posterior tibial 

 nerve in its course along the leg. 



(a) The muscular branches (5 /, 1, 2 s) emanate from the upper part of the nerve 

 either separately or by a common trunk ; one is distributed to each of the deep 

 muscles, viz., the tibialis posticus, the flexor longus digitorum, and the flexor longus 

 hallucis ; and a second nerve is furnished to the soleus, piercing the deep surface 

 of the muscle. 



(&) The fibular branch is a long slender offset which arises in common with the 

 nerves to the deep muscles, and descends, beset with numerous Pacinian corpuscles, 

 in the canal of the peroneal vessels as far as the ankle. It gives off filaments to the 

 vessels which it accompanies, to the shaft of the fibula with the medullary artery, 

 and to the periosteum covering that bone (Rauber). 



(c) The calcaneo-plantar nerve (1, 2s) is given off by the posterior tibial in the 

 lower part of the leg, and becomes superficial by piercing the internal annular 

 ligament. It divides into internal calcaneal branches which ramify in the integu- 

 ment on the inner side of the heel, said. plantar cutaneous branches which supply the 

 skin of the inner and hinder part of the sole. 



(a) One or two articular filaments pass from the posterior tibial nerve close 

 above its division to the inner side of the ankle-joint (Rudinger). 



Internal plantar nerve. The internal plantar (4, 5 /, Is), slightly the larger 

 of the two nerves to the sole of the foot into which the posterior tibial divides, 

 accompanies the internal or smaller plantar artery, and supplies nerves to both sides 

 of the inner three toes, and to one side of the fourth. From the point at which it 

 separates from the posterior tibial nerve, it is directed forwards under cover of the 

 first part of the abductor of the great toe ; then passing between that muscle and 

 the short flexor of the toes, it gives off the internal collateral branch for the great 

 toe, and divides about the middle of the foot into three digital branches. The 

 outermost of these branches communicates with the external plantar nerve. The 

 distribution of this nerve in the foot closely resembles that of the median nerve in 

 the hand. 



Branches. (a} Muscular branches are supplied to the abductor hallucis and flexor 

 brevis digitorum. 



(b) An articular filament passes deeply between the abductor hallucis and the 

 tendons of the long flexors of the toes to supply the joints between the astragalus, 

 the navicular, and the inner two cuneiform bones (Rudinger). 



(c) Small plantar cutaneous branches perforate the plantar fascia to ramify in the 

 integument of the sole of the foot. 



(d) The digital branches are named numerically from within outwards : the 

 outer three pass from under cover of the plantar fascia near the clefts between the 

 toes. The first or innermost branch continues single, but the other three 

 bifurcate to supply the adjacent sides of two toes. They are distributed as follows : 



Theirs/ digital branch is destined for the inner side of the great toe ; it becomes 

 subcutaneous farther back than the others, and sends off a branch to the flexor brevis 

 hallucis muscle. 



The second branch, having reached the interval between the first and second 

 metatarsal bones, furnishes a small twig to the first lumbricalis muscle, and bifurcates 

 behind the cleft between the great toe and the second to supply their contiguous 

 sides. 



The third digital branch, corresponding with the second interosseous space, 

 divides in a manner similar to that of the second branch into two offsets for the sides 

 of the second and third toes. 



VOL. III., PT. 2. Y 



