334 



THE SPINAL NERVES. 



The fourth digital branch, distributed to the adjacent sides of the third and 

 fourth toes, usually has a communication with the external plantar nerve. 



Along the sides of the toes, cutaneous and articular filaments are given from these 

 digital nerves ; and, opposite the ungual phalanx, each sends a dorsal branch to the 

 pulp beneath the nail, and then runs on to the ball of the toe, where it is distributed 

 like the nerves of the fingers. Pacinian corpuscles are attached at intervals to these 

 nerves. 



External plantar nerve. The external plantar nerve (1, 2s) completes the 

 supply of digital nerves to the toes, furnishing branches to the little toe and half 

 the fourth ; it also gives a deep branch of considerable size, which is distributed to 

 several of the short muscles in the sole of the foot. There is thus a great resemblance 

 between the distribution of this nerve in the foot and that of the ulnar nerve in the 

 hand. 



Fig. 217. SUPERFICIAL AND DEEP DISTRIBUTION OK THE PLANTAR 

 NERVES. (After Hirschfeld and Leveille, slightly modified.) 

 (Allen Thomson.) ^ 



Parts of the flexor brevis digitoruin, abductor hallucis, abductor 

 minimi digiti, and the tendons of the flexor longus digitorum, together 

 with the lumbricales muscles, have been removed so as to bring into 

 view the adductor transversus and interosseous muscles in the middle 

 of the foot. 



a, upon the posterior extremity of the flexor brevis digitorum, near 

 which, descending over the heel, are seen ramifications of the calcaneal 

 branch of the posterior tibial nerve ; b, abductor hallucis ; c, tendon 

 of the flexor longus digitorum, divided close to the place where it is 

 joined by the flexor accessorius ; d, abductor minimi digiti ; e, tendon 

 of the flexor longus hallucis between the two portions of the llexor 

 brevis hallucis ; 1, internal plantar nerve giving twigs to the abductor 

 hallucis, and 1', a branch to the flexor brevis digitorum, cut short ; 

 2, inner branch of the internal plantar nerve, giving branches to the 

 flexor brevis hallucis, and forming 2', the internal collateral nerve of 

 the great toe ; 3, continuation of the internal plantar nerve, dividing 

 into three branches, which form, 3', 3', 3', the plantar digital nerves 

 of the first and second, second and third, and third and fourth toes ; 



4, external plantar nerve ; 4', its branch to the abductor minimi digiti ; 



5, twig of union between the plantar nerves ; 6, superficial branch of 

 the external plantar nerve, dividing into 6', 6', the collateral digital 

 nerves of the fourth and fifth toes and the external nerve of the fifth ; 

 7, deep branch of the external plantar nerve. 



The external plantar nerve runs obliquely forwards 

 towards the outer side of the foot, along with the external 

 plantar artery, between the flexor brevis digitorum and 



the flexor accessorius, as far as the interval between the former muscle and the 

 abductor of the little toe. Here it divides into a superficial and a deep branch, 

 having previously furnished offsets to the abductor minimi digiti and the flexor 

 accessorius, as well as a filament through the last muscle to the calcaneo-cuboid 

 articulation (Riidinger). 



(a) The superficial portion separates into two digital branches, which have the 

 same general arrangement as the digital branches of the internal plantar nerve. The 

 outermost of these is undivided, and runs along the outer side of the little toe : it is 

 smaller than the other, and pierces the plantar fascia farther back. The short flexor 

 muscle of the little toe, and sometimes one or both of the interosseous muscles of 

 the fourth space, receive branches from this nerve. 



The larger digital branch usually communicates with the internal plantar nerve, 

 and bifurcates near the cleft between the fourth and fifth toes to supply one side of 

 each. 



(I) The deep or muscular part of the external plantar nerve dips into the sole of 

 the foot with the external plantar artery, under cover of the tendons of the flexor 



