THE UPPER LIMB 4^9 



to belong to the middle and ring fingers, and those of the posterior pair to 

 the index and little fingers. 



The deep muscles of the front of the forearm are next to be dissected, namely, 

 the flexor profundus digitorum, flexor longus polUcis, and pronator quadratus. 

 The anterior interosseous nerve and artery, the latter having two venae comites, 

 are to be followed down the front of the interosseous membrane beneath the 

 pronator quadratus. In this latter situation the nerve should be shown to 

 supply the pronator quadratus, and give an articular branch to the wrist- 

 joint. The artery should be here shown to divide into anterior and pos- 

 terior branches, the former descending to take part in the anterior carpal 

 rete, and the latter piercing the interosseous membrane to reach the posterior 

 carpal rete. 



Front of the Hand. — The various landmarks are to be carefully studied. 

 Thereafter the skin is to be removed by a median incision from the centre of 

 the wrist to the cleft between the middle and ring fingers, and a transverse 

 incision across the roots of the fingers. Median incisions are also to be made 

 down the centre of the thumb and each finger, and the skin removed from these 

 parts. In removing the skin from the palm fibrous processes will come into 

 view, which connect it with the central division of the palmar fascia. The 

 lobulated condition of the superficial fascia of the palm is to be noted, and the 

 superficial transverse ligament is to be looked for as a few scattered transverse 

 fibres lying within the skin at the roots of the fingers. The palmar cutaneous 

 branches of the median and ulnar nerves are to be followed out, and twigs of 

 the radial ners-^e, reinforced by tAvigs from the musculo-cutaneous, are to be 

 shown over the thenar eminence. The palmaris brevis muscle is to be care- 

 fully dissected, as it is subcutaneous and arranged in bundles. The expansion 

 from the tendon of the flexor carpi ulnaris to the anterior annular Ugament is 

 to be noted, as well as the pisi-uncinate and pisi-metacarpal expansions, which 

 are known as ligaments. The ulnar artery and nerve are then to be followed 

 over the anterior annular Ugament till they disappear beneath the palmaris 

 brevis, and their relation to the pisiform bone and hook of the unciform are 

 to be noted. 



The palmar fascia should now receive careful attention. Its thenar 

 and h>*pothenar divisions, which are thin, are to be noted, but attention 

 is to be concentrated on the central division. Its triangular shape, great 

 strength, and the longitudinal direction of most of its fibres are to be observed. 

 Some of the fibres, however, will be seen to be disposed transversely, especially 

 towards the roots of the fingers. In this latter situation it should be shown 

 dividing into four digital processes, which pass to become incorporated with 

 the sheaths of the flexor tendons of the inner four fingers. The thenar and 

 hypothenar divisions of the fascia are removable with ordinary care in order to 

 expose the muscles, and no important structure is in danger. The central 

 division, however, must be removed with the greatest care. In doing so the 

 dissector should particularly note its great strength, which will show him 

 how it would resist the pointing of a palmar abscess, and the necessity of early 

 incision to give vent to the pus. As this division is being removed a deep 

 lateral expansion is to be looked for at either side of it, these expansions 

 passing to join the more deeply placed interosseous fascia. The result 

 is that a great central fibrous tunnel is formed in the palm, which contains 

 the superficial palmar arch, digital arteries and nerves, and flexor tendons, all 

 enclosed in the great palmar bursa. In reflecting the digital processes of the 

 central division deep lateral expansions should be looked for, which, along 

 with them and the anterior fibrous plates of the metacarpo-phalangeal joints, 

 form short tunnels for each pair of flexor tendons. 



On removal of the central division of the palmar fascia the great paln\ar 

 bursa is to be thoroughly mastered. The superficial palmar arch is then 

 to be dissected, and its position and branches are to be carefully studied. 

 The profunda branch is to be shown coming off from the commencement 

 (inner part) of the arch, and, along with the deep division of the ulnar nerve, 

 it will be seen to disappear between the abductor, and flexor brevis, minimi 

 digiti. Four digital arteries are to be followed from the convexity of the 



