192 THE SUPERIOR EXTREMITY 



The branches which spring from the radial artery in this 

 part of its course are of small size. They are : 



1. Ramus carpeus dorsalis. 



2. Aa. metacarpeae dorsales. 



3. Aa. digitales/Two dorsal arteries of the thumb. 



dorsales. (One dorsal artery of the index digit. 



The dorsal radial carpal artery takes origin on the lateral 

 aspect of the wrist, and runs medially, upon the carpus, to join 

 the corresponding carpal branch of the ulnar artery. The arch 

 thus formed is placed under cover of the extensor tendons, and 

 gives off two branches which run distally in the third and 

 fourth inter-metacarpal intervals. They are termed the second 

 and third dorsal metacarpal arteries. 



The first dorsal metacarpal artery arises, as a rule, from the 

 radial trunk, although not infrequently it may be seen to 

 spring from the dorsal carpal arch. It extends distally in 

 the second interosseous space. 



The three dorsal metacarpal arteries are brought into 

 connection with the arteries in the palm by communicating 

 branches. They are joined by the three perforating twigs of 

 the deep volar arch, which make their appearance on the 

 dorsum of the hand between the heads of the medial three 

 dorsal interosseous muscles. Further, at the distal ends of the 

 interosseous spaces the dorsal metacarpal arteries usually send 

 distal perforating branches to join the corresponding common 

 volar digital arteries in the palm. 



The two dorsal arteries of the thumb run distally one 

 upon each side of that digit. 



The dorsal artery of the index is distributed on the lateral 

 side of the index finger. 



Dissection. The limb should now be turned round, so that 

 the transverse metacarpal ligament which stretches across the 

 volar aspects of the heads of the metacarpal bones may be 

 examined previous to the dissection of the interosseous muscles. 



Ligamentum Capitulomm Transversum. The transverse 

 ligament of the heads of the metacarpal bones is a strong 

 band, composed of transverse fibres, which crosses the volar 

 aspects of the heads of the four metacarpal bones of the fingers. 

 Commencing on the lateral side, upon the distal extremity of 

 the index metacarpal, it ends at the medial margin of the 

 hand, upon the head of the metacarpal bone of the little finger. 



