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MUSCLES OF THE HAND. 



these origins are separated by a fibrous arch, 

 through which the radial artery passes ; they 

 are large and fleshy, and soon unite, forming a 

 triangular flattened muscle, which is inserted 

 into the external side of the first phalanx. The 

 insertion of the other muscles are, the two mid- 

 dle into either side of the first phalanx ; they 

 are called the prior and posterior medii; and 

 the last, or posterior annularis, into the inter- 

 nal side of the ring-finger. 



Relations. Posteriorly they correspond to 

 the extensor tendons and skin ; anteriorly they 

 appear beside the palmar interossei, from which 

 they are separated by a strong septum derived 

 from the deep palmar aponeurosis. Their other 

 relations are the same as the palmar interossei. 

 The first, the abductor indicis, corresponds an- 

 teriorly to the adductor pollicis and part of the 

 flexor brevis, which it crosses at right angles ; 

 its inferior and external margin is subcuta- 

 neous. 



Use. They are all abductors of the fingers 

 from the axis of the hand, and by reason of 

 their insertion into the extensor tendons, act 

 best when the hand is extended. The same 

 may be said of the palmar. 



Before we enter on the general uses of this 

 complex muscular apparatus, it would be well 

 to remark that the proper muscles of the thumb 

 and little finger appear to be nothing more than 

 exaggerated and multiplied lumbricales and in- 

 terossei. We may, in this light, view the short 

 flexor of the thumb as the first lumbricalis, its 

 abductor and opponens as a dorsal interosseus, 

 while its adductor would represent a palmar 

 interosseous muscle; again, as regards the little 

 finger, its abductor and short flexor together 

 personate a dorsal interosseus, while its adduc- 

 tor would be but an internal or palmar inter- 

 osseous. Their principal use is, by acting 

 on the carpo-metacarpal articulations of the 

 thumb and little finger, which enjoy freer 

 motion than the intermediate ones, especially 

 that of the thumb, to oppose these extreme 

 points of the hand to each other, more or less 

 increasing its concavity, and thereby giving a 

 firmer grasp, inasmuch as they adapt the cavity 

 of the palm to the volume of the body grasped. 

 The great use of this opposable faculty of the 

 thumb (which action is the peculiar characte- 

 ristic of the hand as distinguishing it from the 

 foot) may be shewn by firmly clenching the fist, 

 when the thumb, by its combined powers of 

 opposition and flexion, is made to overlap the 

 fore and middle, and in some the third fingers, 

 pressing them firmly against the palm, while, 

 at the same time, the thenar eminence is 

 thrown forwards and inwards, meeting them in 

 the palm, and by abutting against counteracts 

 their tendency to fly open when a blow is 

 struck, acting at the same time as a cushion to 

 deaden the violence of the shock. We here 

 see, also, the flexion of the fingers modified by 

 the radial interossei and lumbricales, which, 

 by their action, throw the fingers radiad, so as 

 to bring the three outer ones to abut against 

 the thenar eminence; the little finger is pro- 

 tected, in like manner, by the hypothenar, 

 which is thrown forwards and outwards. The 



converse modification of the flexion of the 

 fingers by means of the ulnar interossei may 

 be seen in the action of the left hand of a 

 fiddler, where the fingers are flexed and pointed 

 ulnad to run up the scale. 



It only remains for us to give a summary 

 view of the muscles, extrinsic and intrinsic, 

 concerned in the motions of the hand. These 

 motions are flexion, extension, adduction or 

 motion ulnad, abduction or motion radiad. 

 First, the flexors of the wrist are six. 1. 

 Flexor longus pollicis ; 2 and 3, flexor sub- 

 limis et profundus ; 4, palmaris longus ; 5, 

 flexor carpi radialis; 6, flexor carpi ulnaris. 

 The extensors are six. 1, Extensor communis; 

 2, indicator ; 3, extensor secundi internodii 

 pollicis; 4 and 5, extensores carpi radiales 

 longior et brevior; 6, extensor carpi ulnaris. 

 The last three of the extensors as well as the 

 last three of the flexors act directly on the wrist ; 

 the others act first on the phalanges. These 

 also are the muscles that, in extreme flexion 

 and extension, call into play the motion that 

 exists between the two rows of the carpus, the 

 two former extending, the three latter flexing 

 the second row upon the first. 



The adductors are five. 1. Extensor carpi 

 ulnaris ; 2, extensor communis ; 3, flexor carpi 

 ulnaris ; 4, sublimis ; 5, profundus. 



The abductors are also five. 1 and 2, Ex- 

 tensores ossis metacarpi et primi internodii 

 pollicis; 3 and 4, extensores carpi radiales 

 longior et brevior ; 5, flexor carpi radialis. 



The following table is intended to exhibit at 

 one view the motions of which the fingers are 

 capable, and the muscles which effect them. 



The movements of the fingers are 



1. Flexion performed by nine. 

 Flexor longus pollicis. 

 Flexor sublimis. 



Flexor profundus. 



Three internal lumbricales. 



Three interossei in tern i. 



2. Extension by eight. 

 Three extensores pollicis. 

 Extensor communis. 

 Indicator. 



Three internal dorsal interossei. 



3. Adduction by seven. 



Three adductor, flexor brevis, and oppo- 

 nens pollicis. 



Abductor minimi digiti. 



Three interossei, viz. posterior indicis, 

 posterior medii, posterior annularis. 



4. Abduction by eleven. 

 Abductor pollicis. 



Adductor et opponens minimi digiti. 

 Four lumbricales. 



Four interossei, viz. abductor indicis, prior 

 medii, prior annularis, interosseus au- 

 ricularis. 



We thus see that the hand is furnished with 

 no less than thirty-three muscles, each capable 

 of acting either singly or in conjunction with 

 others. The most powerful of these are the 

 flexors and opposers, both performing actions, 

 as we have seen, peculiarly adapted for the pre- 

 hension and retention of bodies. 



But there is yet another function in which 



