THE ANTERIOR TIBIAL NERVE. 



337 



number of toes supplied by the musculo-cutaneous nerve is seldom increased. (On variations 

 in the nerves of the dorsum of the foot, and their relative frequency, see the Second Annual 

 Report of the Committee of Collective Investigation of the Anat. Soc.. by Arthur Thomson , 

 Joura. Anat., xxvi, 1891.) 



Anterior tibial nerve. The anterior tibial nerve (n. peroneus profundus) 

 (4, 5 /, 1 s\ commencing between the fibula and the peroneus longus, inclines 

 obliquely beneath the long extensor of the toes to the fore part of the interosseoua 

 membrane, and there comes into contact with the anterior tibial vessels ; with 

 these vessels it descends to the front of the ankle-joint, where it divides into an 

 external and an internal branch. The nerve reaches the anterior tibial artery about 



Fig. 219. DISTRIBUTION OP THE BRANCHES OP THE EXTERNAL 



POPLITEAL NERVE ON THE FRONT OP THE LEG AND DORSUM OP 



THE FOOT. (After Hirschfeld and Leveille.) 1 



The upper part of the peroneus longus muscle has been removed, the 

 tibialis anticus, the long extensor of the great toe and the peroneus 

 longus are drawn apart in the leg by hooks marked a, b, and c, and 

 the tendons of the extensor muscles have been removed on the dorsum 

 of the foot ; 1, external popliteal or peroneal nerve, winding round the 

 outer part of the fibula ; 1', its recurrent articular branches exposed 

 by the dissection of the upper part of the tibialis anticus muscle ; 

 2, 2, musculo-cutaneous nerve ; 2' 2', twigs to the long and short 

 peroneal muscles ; 3, 3', internal branch of the musculo-cutaneous 

 nerve ; 4, 4', 4', its external branch ; 5, external saphenous nerve, 

 uniting at two places with the outer branch of the musculo-cutaneous ; 

 5', its branch to the outer side of the fifth toe ; 6, placed on the upper 

 part of the extensor longus digitorura, marks the anterior tibial nerve 

 passing beneath the muscle ; 6, placed farther down on the tendon of 

 the tibialis anticus, points to the nerve as it lies in front of the 

 anterior tibial artery ; 6', 6', its muscular branches in the leg ; 6", on 

 the tendon of the extensor longus hallucis, points to the anterior tibial 

 nerve after it has passed into the foot behind that tendon ; 7, its inner 

 branch, uniting with a twig of the musculo-cutaneous, and giving the 

 dorsal digital nerves to the adjacent sides of the first and second toes ; 

 8, distribution of its outer branch to the extensor brevis digitorum and 

 tarsal articulations. 



the junction of the upper with the second fourth of the 

 leg, and is thence placed in front of the vessels as far as 

 the ankle, at which spot it is usually on their outer side. 

 Branches. (a) Muscular branches. In its course 

 along the leg, the anterior tibial nerve gives offsets to 

 the adjacent muscles, namely, the tibialis anticus, the 

 extensor longus digitorum, the extensor proprius hallucis, 

 and the peroneus tertius. 



(b) An articular filament for the ankle-joint arises 

 from the lower part of the nerve. 



(c) The external branch of the anterior tibial nerve 



turns outwards over the tarsus beneath the short extensor of the toes ; and, having 

 become enlarged (like the posterior interosseous nerve on the wrist) breaks up into 

 branches which supply the short extensor muscle, and the articulations of the foot. 



(d) The internal branch, continuing onwards in the direction of the anterior tibial 

 nerve, accompanies the dorsal artery of the foot to the first interosseous space, and 

 ends in two branches, which supply the integument on the neighbouring sides of the 

 great toe and the second toe on their dorsal aspect. It communicates with the 

 internal division of the musculo-cutaneous nerve. 



From the internal branch one, and from the external two or three slender 

 interosseous branches are sent forwards to the intermetatarsal spaces, where they are 

 joined by the perforating twigs of the external plantar nerve (p. 385). They supply, 



