770 



SPINAL NERVES. 



front of the femur and inner part of the ar- 

 ticulation ; this is the least constant of the 

 branches. The inferior internal articular, the 

 largest of the nerves to the joint, arises rather 

 above the articulation, descends to it, lying 

 external to the vessels, is then directed in- 

 wards, beneath the poplitaeal vessels, and 

 meets with the artery of the same name ; it 

 now lies on the poplitaeus, covered by the 

 fascia, passes beneath the internal lateral liga- 

 ment, winds round the head of the tibia, per- 

 forates the capsule, and supplies the synovial 

 membrane. This branch gives, occasionally, 

 some filaments to the posterior part of the 

 articulation. The last articular branch is the 

 posterior or azygos, which is given off opposite 

 the joint, or from the inferior internal nerve : 

 it perforates the posterior ligament, and is 

 distributed to the articulation."* We have 

 observed this inferior articular nerve give off, 

 occasionally, muscular filaments to the plan- 

 taris, and upper part of the poplitaeus. 



The cutaneous branch is named the tibial sa- 

 phfEnus (external saphaenus communicating 

 saphaenus communicans tibiae), and takes its 

 origin from the back part of the trunk ex- 

 ternal to the muscular branches. It inclines 

 a little to the outside of the middle of the 

 poplitaeal space, under the fascia, but super- 

 ficial to the gastrocnemius, along the posterior 

 surface of which it passes till it perforates the 

 fascia at a variable distance from the ankle, 

 and receives the corresponding branch from 

 the peronaeal saphaenus. It is then directed, 

 under the name of the external sapkcenus, 

 along the outer part of the tendo Achillis 

 to the outer and back part of the external 

 ankle, where it divides into its terminal 

 branches. In the first part of its course it 

 lies to the inside of the external saphaena 

 vein. Near the lower angle of the poplitaeal 

 span it passes in front of the vein to get to 

 its outside, continues external to it as far as 

 about an inch above the outer ankle, and 

 again passes in front of it to its inside. 



The tibial saphaenus gives off no branch till 

 it becomes external saphaenus, and internal 

 and external cutaneous branches arise from 

 it. The internal supply the outer and back 

 part of the leg: and a superior and inferior 

 calcaneal branch are generally observed. The 

 superior is directed over the tendo Achillis, 

 supplies the skin at the inner and back part 

 of the heel, and communicates with filaments 

 from the external plantar : the inferior passes 

 along the outer border of the tendo Achillis 

 to the skin at the outer and lower part of the 

 heel. The outer cutaneous run downwards 

 and forwards over the tendon of the pero- 

 naeus longus, as far as the malleolus externus, 

 communicating above with descending fila- 

 ments of the peronaeal cutaneous ; and below 

 with the malleolar filaments of the musculo 

 cutaneous. Independent of these, cutaneous 

 filaments and a few delicate nerves are given 

 off, which accompany the saphaena vein. 



The terminal branches are composed of a se- 

 ries of cutaneous branches to the back part of 

 * Ellis's Demonstrations of Anatomy, p. 676. 



the ankle, heel, and back part of the outer edge 

 of the foot, and a long nerve, the continuation 

 of the trunk directed along the outer edge of 

 the foot to supply the outer margin of the 

 little toe, communicating previously with the 

 musculo-cutaneous. 



The termination of the tibial saphaenus nerve 

 is subject to considerable variation, both as to 

 size and distribution. It occasionally forms 

 no connection with the peronaeal saphaenus, 

 and then is very large. When united with 

 the peronaeal saphasnus, so as to form the ex- 

 ternal saphaenus, its terminal branch not un- 

 frequently divides into two ; the one division 

 for the opposed edges of the fourth and fifth 

 toe ; the other for the outer edge of the latter. 

 We have observed the saphaenus nerve sup- 

 plying also the opposed edges of the third and 

 fourth toes, whilst the musculo-cutaneous in 

 this instance supplied merely the inner edge 

 of the great toe and the opposed margins of 

 the second and third toes. 



The tibial nerve, before dividing into the in- 

 ternal and external plantar, gives off, a little 

 above the ankle, an internal calcaneal branch, 

 which in a high division of the nerve comes 

 away from the external plantar. Having sup- 

 plied the skin at the inner aspect of the heel, 

 it winds beneath the inferior surface of the os 

 calcis, and communicates with the calcaneous 

 branch of the external saphaenus. 



The internal plantar nerve, larger than the 

 external and analogous to the median nerve 

 in the hand, passes behind the internal malleolus 

 superficial to and distinct from the tendons of 

 the tibialis posticus, and in front of the pos- 

 terior tibial vessels. It then runs above 

 the abductor pollicis, and is directed in the 

 intermuscular septum, between it and the 

 flexor brevis digitorum. Having perforated 

 this, it appears between the two muscles, and 

 divides into internal and external branch es 



The internal branch is smaller than the ex- 

 ternal, passes from without inwards over the 

 tendon of the long flexor of the toe to the 

 inner side of the metatarsal bone, gives fila- 

 ments to the abductor pollicis, flexor brevis, 

 and the skin, and terminates at the inner side 

 of the toe, supplying in its course filaments to 

 the articulations, and when it reaches the last 

 phalanx, a small cutaneous branch to the 

 dorsum. 



The external branch divides after a course of 

 about an inch or two. The internal division, 

 as it is directed along the first interosseous 

 space, gives off in its course filaments to the 

 first interosseous and lumbricalis, and at the 

 anterior part of this space divides into two 

 twigs for the opposed sides of the great and 

 second toe. The external division, after a 

 very short course, divides into two branches : 

 the internal crosses obliquely the second in- 

 terosseous space, gives filaments to the second 

 lumbricalis, and bifurcates at its anterior ex- 

 tremity for the supply of the opposed sides 

 of the" second and third toes : the external 

 crosses obliquely to the third interosseous 

 space, and like the preceding divides at its 

 anterior extremity into two twigs for the 



