520 



MUSCLES OF THE HAND. 



short aponeuroses along all the outer edge ot 

 the first metacarpal bone. 



Relations. \\ith the exception of a small 

 portion of its external border, this muscle is 

 covered anteriorly by the preceding muscle. It 

 covers the anterior surface of the first rneta- 

 carpal bone, and its articulation with the tra- 

 pezium. 



It draws the thumb inwards, turning it upon 

 its own axis, so that it opposes its palmar 

 aspect to the other fingers. 



3. Flexor brevis pollicis mama (trapezo- 

 phalangicti, Cruveilh.) is a larger muscle than 

 the two preceding ones, triangular, bifid supe- 

 riorly, having its anterior surface channelled ; 

 arises by aponeurotic and fleshy fibres, exter- 

 nally from the fore and under part of the 

 annular ligament, and from the process of the 

 trapezium, internally and posteriorly from all 

 the reflected portion of the annular ligament, 

 forming the sheath for the radial flexor and 

 extending to the os magnum, and from the os 

 magnum often by a distinct portion. From these 

 various origins ihe fleshy fibres run downwards 

 and outwards, are more oblique as they are 

 more internal, and terminate in a strong fleshy 

 bundle which is attached to the external sesu- 

 moid bone and outer side of the first phalanx. 



Relations. This muscle is covered by the 

 external palmar aponeurosis, more internally by 

 the tendon of the long flexor of the thumb, then 

 by the common flexor tendons. It covers the 

 first dorsal interosseous, the tendon of the 

 radial flexor of the wrist, and a small portion 

 of the external margin of the adductor of the 

 thumb. Its outer edge corresponds to the 

 abductor and is often confounded with the 

 opponens, and its inner would be undistin- 

 guishable from the abductor near the first meta- 

 carpal bone, if it were not separated from it by 

 the arteria magna pollicis,* a fact that appears 

 to have been overlooked by many anatomists, 

 or the descriptions of the attachments of this 

 muscle would never have been so much at 

 variance : the foregoing description coincides 

 with that of Meckel and Cruveilhier. Its 

 tendon of insertion is covered by that of the 

 abductor, which is external to it. 



This muscle is badly named, at least if 

 names be intended to denote action, for its 

 power of flexing the thumb is very slight ; but 

 it has considerable power as an opposer of it, 

 its insertion being especially favourable to that 

 action . 



4. Adductor pollicis miimis (nietacarpo-pha- 

 langicn du poucc, Chauss.) is the largest muscle 

 of the thumb as well as the most internal ; in 

 shape it is a perfect triangle, arising from all 

 tin; anterior border of the third metacarpal 

 bono, from its articulation with the magnum, 

 from the anterior and superior portion of the 

 trapezoid, and from the palmar interosseous 

 aponeurosis in its central portion. From this 

 extensive attachment the fibres run transversely 

 < utwards, the superior ones being most oblique; 

 tl.< \ t-unvrrjje to a strong fleshy bundle, which 



' Also deep in the palm, it is generally sepa- 

 ' ' rd fjom the adductor by the deep palmar areh. 



is inserted by means of the internal sesamoid 

 bone into the first phalanx of the thumb. 



Relation*. Its two internal thirds are covered 

 by the lumbricales and common flexor tendons, 

 also by a layer of the deep interosseous apo- 

 neurosis which constitutes its sheath. It covers 

 the two first interosseous spaces. Its inferior 

 border is subcutaneous, especially posteriorly, 

 where it may be felt in the fold of skin extend- 

 ing from the index finger to the thumb.* 



Its name implies its action ; it draws the 

 thumb towards the median line of the hand. 



b. Muscles of the internal palmar region. 

 There are four muscles in this region also; one 

 is a cutaneous muscle, the palmaris brevis ; the 

 others are proper to the little finger, and are 

 inserted into the inner side of its first phalanx 

 and the fifth metacarpal bone. They consist, 

 as the last described set, of an abductor, short 

 flexor, and an opponens minimi digiti. 



1. Palmaris brevis (peancier lie la main, 

 Cruveilh.) This muscle when it exists, (for in 

 weakly subjects its fibres are often not to be 

 distinguished, though on the other hand it 

 acquires considerable volume in those that are 

 muscular,) arises by aponeurotic intermingled 

 with fleshy fasciculi which run horizontally 

 inwards, forming a small quadrilateral muscle 

 which terminates in the skin. 



Relations. Covered by the skin and im- 

 bedded in the adipose substance, it is spread 

 over the muscles of the little finger and the 

 ulnar artery and nerve, from which it is sepa- 

 rated by the internal palmar aponeurosis. 



It increases the concavity of the palm by 

 puckering the skin over the part it occupies, 

 thereby drawing the hypothenar eminence for- 

 wards and outwards, and rendering it more 

 convex. 



2. Abductor minimi digiti (pisi-jilmliingien, 

 Cruveilh.) A long flat muscle, broadest at its 

 centre, arising from the pisiform bone and from 

 an expansion of the flexor carpi ulnaris, by 

 strong aponeurotic fibres, which soon become 

 fleshy, running along the inner edge of the 

 fifth metacarpal bone. It ends in a flattened 

 tendon, which is inserted in common with the 

 short flexor into the inner side of the first 

 phalanx, sending an expansion into the extensor 

 tendon. 



Relations. It is covered by the internal 

 palmar aponeurosis, itself covering the oppo- 

 nens. 



Use. It draws the little finger inwards and 

 forwards, separating it from the others. 



* Sometimes this muscle is separated into two 

 bellies, tbe one superior and the other inferior, 

 which are completely separate from each other, 

 and of which the superior is by far the greater. Ill 

 this case the first arises solely from the os magnum 

 or from this bone and a small portion of the 

 superior extremity of the thiid metacarpal bone, 

 while the second arises irom the inferior portion of 

 the anterior head of the third, fourth, and some- 

 times even the fifth metacarpal bones; it runs 

 transversely outwards and a little backwards to 

 meet the superior head at the first phalanx of the 

 thumb. This anomaly resembles tbe normal con- 

 dilion of the transverse and oblique adductors of 

 the great toe. Meikcl, Anal. vol. ii. p. 165. 



