Limbs : Upper Limb 



mally from the phalanx to the meta- 

 carpal while its origin has grown round 

 the flexor sheath on to the annular 

 ligament. 



A palmar ridge is seen running along 

 each of the shafts, made by the meeting 

 of the interosseous surfaces on the 

 palmar aspect : it may be slightly dis- 

 placed to the inner side in the fourth and 

 fifth bones * as a result of their having 

 a palmar interosseous on the radial 

 side, but a displacement in the opposite 

 direction is not apparent on the index 

 metacarpal. 



The ridge is widened in the middle 

 metacarpal by the origin of Adductor 

 transversus from it. On this bone, and 

 on that of the Index, the ridges are 

 not as a rule so clearly carried to the 

 bases, but are interrupted by an ill- 

 defined groove that marks the situa- 

 tion of the deep palmar arch : on their 

 bases, proximal to this, the Adductor 

 obliquus has part of its origin. 



It is apparent from the markings 

 for the interossei (Fig. 92) that these 

 muscles form thick masses which practically cover in the bones on their palmar aspects 

 and, with the Adductors in the outer part of the palm, separate them from the flexor 

 sheath. Dorsally, however, the distal two-thirds or more of the shafts are not covered 

 by the muscles, and here the shaft is broad and flat and in relation with the extensor 

 tendons of the fingers. 



A summary of the muscles that take origin from the different metacarpals, and the 

 tendons inserted into them, may not be out of place here. 



FIG. 93. To show the relation of the tendons, etc., 

 on the dorsum to the underlying carpal bones and 

 to each other. The radial artery and posterior 

 carpal arch are also shown. 



TENDONS. 



Ext. ossis metacarp. 



METACARPAL. MUSCLES. 



First . . Flexor brevis (deep head) . 



Opponens (insertion). 



First dorsal interosseous. 

 Second . . First and second dorsal inteross. . 



First palmar inteross. . 



Adductor obliquus 

 Third . . Second and third dorsal inteross. 



Adductor transversus . 



Adductor obliquus. 

 Fourth . . Third and fourth dorsal inteross. 



Second palmar inteross. 

 Fifth . . Fourth dorsal inteross. 



Third palmar inteross. 



Opponens (insertion). 



* Like the other characters described in these bones, these varieties should be studied in well-marked 

 and good-sized male bones : they are not striking, or even apparent, in small and feeble bones. 

 F.A. 8 



Flexor carpi radialis. 

 Extensor c. rad. long. 

 Extensor c. rad. brev. 

 Flexor c. rad. 

 Ext. c. rad. brev. 



Extensor carpi ulnaris. 



