SYMPATHETIC XERVES 819 



pierce the internal annular liganjent, accompanying the branches of the internal 

 calcanean artery, and are distrilnited to the thick fascia and integument which 

 covers tlie heel and adjacent part of the sole. 



(2) The internal plantar nerve is formed of fibres from the fourth and fifth 

 lumbar, and the first and second sacral nerves. It is the larger of the two terminal 

 branches of the posterior tibial, and corresponds in its distribution to the median 

 nerve in the hand. It runs forwards in the interval between the abductor hallucis 

 and the flexor brevis digitorum; gives off branches to supply both these muscles, 

 and a number of cutaneous twigs which appear in the interval between the middle 

 and internal parts of the plantar fascia. It also sup^dies the astragalo-navicular 

 and the internal intercuneiform joints. Near the level of the tarso-nietatarsal 

 articulation it terminates l:)y dividing into four digital Ijranches. The first digital 

 branch gives off a branch to supply the flexor brevis hallucis, and then runs along 

 the inner side of the great toe as far as the extremity of that digit. The second 

 branch gives off a twig to supply the first or innermost lumbrical muscle, and then 

 divides into two collateral branches which supjdy the adjacent sides of the great and 

 second toes. The third branch divides in a similar manner to supply the contigu- 

 ous sides of the second and third toes. The fourth branch communicates with tlie 

 superficial di\'ision of the external plantar, and divides to supply tlie adjacent sides 

 of the third and fourth toes. The muscular twigs to the flexor 1:)revis hallucis and 

 the first lumbrical muscle contain fibres from the fifth lumbar and first sacral 

 nerves. 



(3) The external plantar nerve is formed by fibres of the first and second 

 sacral nerves. It shows many points of resemblance to the distribution of the 

 ulnar nerve in the hand. From its origin, at the temiination of the posterior til)ial 

 nerve, it is directed outwards and forwards between the flexor brevis digitorum and 

 the flexor accessorius. In this part of its course it supplies the accessorius, the 

 al)ductor minimi digiti, and the calcaneo-cuboid joint. It is then directed forwards 

 in the interval between the last-named muscle and the flexor brevis digitorum, and 

 terminates at the level of the tarso-metatarsal articulations by dividing into a super- 

 ficial and a deep division. Previous to its division it gives oft' several cutaneous 

 twigs, which appear in tlie inter\'al between the middle and external divisions of the 

 plantar fascia. The superficial division divides into two digital nerves, an exter- 

 nal and an internal. The internal branch supplies the interosseous muscles which 

 occupy the fourth interosseous space, and, having communicated with the internal 

 plantar, divides into two collateral branches which supply the contiguous sides of 

 fourth and fifth toes. The external branch supplies the flexor brevis minimi 

 digiti, and is then directed along the f)Uter border of the little toe to terminate at 

 the extremity of that digit. The deep division of the external plantar nerve runs 

 inwards and forwards on the dorsal or deep surface of the flexor tendons, and rami- 

 fies in the interval between these tendons and the interosseous muscles. It sup- 

 plies the three outer lumbrical muscles, the interosseous muscles occupying the 

 three inner interosseous spaces, the transvcrsus pedis, and the adductor hallucis. 

 and it gives branches to the adjacent articulations. 



Table Showing Relations of Lumbar and Sacral Xerves to Branches ov 



Lumbar and Sacral Plexuses 

 XicKVE Roots. Nekves. 



I J r Ilio-hypogastris 



(. ,, inguinal 



1 and 2 1 Genito-crural 



2 and 3 L External cutaneous 



2, 3, and 4 1 .[ Anterior crural 



' ' ( Ol»turator 



4, 5 L. , and IS / ^npoi'ior gluteal 



I Xerve to quadratus femoris 



4, 5 L., land 2 S Gt. sciatic (ext. poplit. i)art) 



4, 5 L., 1. 2, and 3 S Qt. sciatic (int. poplit. part) 



