REGIONS OF THE HAND. 



525 



The annular ligament gives attachment inferiorly 

 on either side to the muscles of the thumb and 

 little finger, and in the centre to the palmar 

 fascia, a dense fibrous layer binding down the 

 flexor tendons in their passage along the hand. 

 The palmar fascia is chiefly derived from 

 the expansion of the palmaris longus, which, 

 when present, is its tightening muscle. It 

 is strongest in the palmar hollow, where it 

 is triangular in shape, its apex at the an- 

 nular ligament, and is composed of divergent 

 and longitudinal, interwoven with a few trans- 

 verse fibres; the latter, becoming gradually 

 fewer and more scattered, are lost on the 

 tendons running to the fingers, and some few 

 are at times continuous with the tendinous 

 sheaths of the fingers. Near the roots of the 

 fingers this portion of the palmar fascia divides 

 into four bands, which subdivide each into two 

 tongue-like processes, that embrace the heads 

 of the metacarpal bones, and are attached to 

 the sides of the first phalanges and the inferior 

 transverse metacarpal ligament. At this point 

 of division the transverse fibres are stengthened, 

 and convert these slits into four distinct fibrous 

 arches, through which pass the flexor tendons. 

 Between these arches we find three lesser ones 

 resulting from the primary division of the fascia. 

 They transmit the collateral vessels and nerves, 

 and the lumbricales. This fascia is intimately 

 connected with the preceding layer anteriorly, 

 its deep surface covering the superficial palmar 

 arch, flexor tendons, ulnar and median nerves, 

 from which it is separated by loose and very 

 extensible cellular tissue, which permits the 

 tendons to play freely. This portion of the 

 fascia presents numerous apertures through 

 which the deep fat and cellular tissue commu- 

 nicate with the subcutaneous, and when the 

 parts beneath are swollen they protrude, form- 

 ing small hernise, which, getting strangulated in 

 these apertures, give rise to great pain. It de- 

 taches from either side two processes, a superfi- 

 cial and a deep one. The two deep processes 

 dive deep into the palm, to form the mterosseous 

 aponeurosis ; of the superficial ones, the exter- 

 nal, assisted by the tendinous expansion of the 

 extensor ossis metacarpi, envelopes the thenar 

 muscles; the internal stronger, and assisted by 

 the flexor carpi ulnaris expansion, encloses 

 the hypothenar muscles, and to it is attached 

 the palmaris brevis. We next meet with the 

 strong sheaths binding down the flexor tendons 

 in their passage along the fingers. They are 

 continuous above with the palmar fascia, by 

 means of strong detached transverse fibres, 

 which are prolonged over the tendons as they 

 pass through the arches of the fascia; laterally 

 they are firmly attached to the ridges on the 

 sides of the phalanges. On the bodies of the 

 two first phalanges these sheaths are very 

 strong and resisting; but opposite the articula- 

 tions they become very thin, and are often 

 wanting; so that the synovial sacs of the ten- 

 dons are in contact with the subcutaneous layer; 

 and it is through these spaces that the inflam- 

 mation in whitlow is propagated to the synovial 

 membrane and joints. At the last joint of the 

 fingers they become weak and thin, and are 



confounded with the* pulp and periosteum. 

 They each enclose a distinct elongated synovial 

 sac, which reaches as far upwards as the fibrous 

 arch of the fascia, but does not communicate 

 with the synovial membranes of the joints, en- 

 tirely enveloping the flexor tendons, lubricating 

 them, and facilitating these motions in the 

 sheaths. At the point where the tendon of the 

 profundus passes through the divisions of the 

 sublimis, there is a falciform process of the 

 synovial sheath of considerable strength, at- 

 taching the tendon of the latter to the first pha- 

 lanx, so that if the fingers be amputated at the 

 second joint, the power of moving the first 

 phalanx will still be retained, though the con- 

 trary has been stated. We may here likewise 

 notice that the gradual contraction of the three 

 last fingers occurring in adults, (crispatura ten- 

 dinum,} formerly thought incurable, as it was 

 supposed to be the result of a drying or con- 

 traction of the tendons, is stated by Baron 

 Dupuytren to be nothing more than a band or 

 strip of the palmar fascia, adhering to the 

 sheath of the tendon, upon the division of 

 which a complete cure may be effected ; or it 

 may be caused by a fibrous transformation of 

 the subcutaneous cellular layer, depriving it of 

 its elasticity, and causing it to contract, so that 

 the finger cannot be extended. What favours 

 this opinion is, that this malady generally oc- 

 curs in labourers, boatmen, and those whose 

 avocations necessitate constant flexion of the 

 fingers, at the same time that firm pressure is 

 kept up, especially against the roots of the 

 three inner fingers, as in handling a spade, or 

 grasping an oar. 



4. The vessels and nerves are exposed on 

 removing the fascia, being immediately under- 

 neath it. The palmar aspect of the hand being 

 that of flexion, according to the general rule of 

 arterial distribution, the principal trunks are 

 there found; they are the ulnar and radial 

 arteries, and a branch of the interosseous ac- 

 companying the median nerve. 



The ulnar artery at the wrist lies on the 

 annular ligament, to the radial side of the pisi- 

 form bone, where it is covered by the expan- 

 sions of the flexor carpi ulnaris ; it then curves 

 towards the mesial line, and crossing the annu- 

 lar ligament, traverses the palm between the 

 fascia and the flexor tendons, in a curved direc- 

 tion towards the centre of the metacarpal bone 

 of the index finger. In this course it forms an 

 arch, the convexity of which looks downwards 

 and inwards, towards the ring and little fingers, 

 its concavity being turned to the ball of the 

 thumb. It then inosculates with two branches 

 from the radial, the superficialis volse, and the 

 radialis indicis, forming thus the superficial 

 palmar arch, from the convexity of which pro- 

 ceed four digital arteries which subdivide into 

 the collateral branches at about two lines below 

 the metacarpo-phalangean articulations; they 

 supply the palmar and lateral surfaces of all the 

 fingers except the thumb and the radial side of 

 the index finger. They all run along the sides 

 of the fingers external to the sheaths, to the 

 last phalanx, where those of either side coalesce, 

 forming an arch, from which arise numerous 



