THE LOWER LIMB 607 



entering the innermost lumbricalis, whilst the other three will be found to 

 receive their nerve-supply from the deep part of the external plantar nerve. 

 The internal plantar nerve is now to be dissected, as well as the internal 

 plantar artery. The small size of the artery and the large size of the nerve 

 are to be noted, and each is to be followed out to its distribution. The 

 external plantar artery and nerve are next to be dissected in the first part 

 of their course as they cross the sole from within outwards. The large size 

 of the artery is to be noted, and the nerve is to be sho\vn suppl>-ing the mus- 

 culus accessorius and abductor minimi digiti, besides giving off articular and 

 cutaneous branches. The superficicil terminal branch of the external plantar 

 nerve is also to be followed out, showing its two digital nerves, the outer- 

 most of which suppUes the flexor brevis minimi digiti, and, as a rule, the 

 interosseous muscles of the fourth space. The tendons of the flexor longus 

 hallucis and flexor longus digitorum and the musculus accessorius are now 

 to be divided near the ankle and turned forwards, but the plantar vessels 

 and nerves are to be left undisturbed. 



The dissector is then to display the third layer of muscles in the following 

 order from within outwards : flexor brevis hallucis, adductor obhquus hallucis, 

 and flexor brevis minimi digiti. Ljing across the heads of the four outer 

 metatarsal bones will be found the adductor transversus haUucis (transver- 

 saUs pedis). In dissecting the flexor brevis hallucis its single origin and double 

 insertion are to be noted, and a sesamoid bone is to be looked for in each head 

 of insertion. Its nerve is to be found coming from the first or most internal 

 digital branch of the internal plantar. The nerve of the adductor obUquus 

 hallucis is to be found coming from the deep part of the external plantar nerve. 

 In dissecting the flexor bre\is minimi digiti care must be taken to sepsirate 

 it from the most external plantar interosseous, close to which it Ues, and with 

 which it is apt to be confounded. Its nerve is usually to be found coming 

 from the outer digital branch of the superficial part of the external plantar. 

 In dissecting the adductor transversus hallucis it should be noted that the 

 digital nerves on their way to the toes Ue superficial to the muscle, whilst 

 the digital vessels Ue on its deep surface. The nerve-supply of this muscle is 

 to be found coming from the deep part of the external plantar. The dissector 

 should now show the relation of muscles which take insertion into the base 

 of the first phalanx of the great toe, as follows: inner side — abductor hallucis 

 and inner head of flexor brevis hallucis ; outer side^ — outer head of flexor 

 brevis hallucis, adductor obhquus hallucis, and adductor transversus hallucis. 

 The plantar triangle and its contents should next be examined. 



The further stage of the dissection of the sole consists in dividing the 

 flexor brevis hallucis and adductor obhquus hallucis, in order to expose 

 (i) the deep parts of the external plantar artery and nerve, (2) the plantar 

 (and dorsal) interossei muscles, and (3) the plantar or perforating branch of 

 the arteria dorsahs pedis. In the case of the deep part of the external plantar 

 nerve, muscular, articular, and perforating branches are to be looked for. It 

 is to be noted that the deep part of the external plantar nerve gives branches 

 to the outer three lumbricales. In the case of the deep part of the external 

 plantar artery the plantar arch and its branches are to be dissected. The 

 plantar or perforating branch of the arteria dorsahs pedis is to be found 

 appearing at the proximal part of the first interosseous space, and the following 

 branches are to be dissected, namely, arteria magna or princeps hallucis, and 

 communicating to the plantcir arch. 



The external plantar arter>- and nerve may now be cut to enable them to 

 be laid fully aside, and the plantar interosseous muscles are to be dissected. 

 Care must be taken not to confoimd the most external plantar interosseous 

 with the flexor brevis minimi digiti. At this stage of the dissection the inser- 

 tion of the lumbricales is to be studied. The innervation of the interossei will 

 be found to come from the deep part of the external plantar nerve, except in 

 the case of the interossei of the fourth space, which usually get their nerve- 

 supply from the outer digital branch of the superficial part of the external 

 plantar. The dissector should now revise the insertion of all the tendons 

 connected \vith the foot, and, if any have not yet been followed out to their 



