652 THE ARTERIES. 



the capsular ligament of the carpal articulations, after anastomosing on the 

 inner side with the divisions of a branch furnished by the posterior radial artery, 

 and on the outside with the ramifications from the interosseous artery of the 

 forearm. 



These terminal ramuscules are distributed to the carpal articulation, or the 

 sheaths of the extensor tendons, and communicate with the dorsal interosseous 

 metacarpal arteries. 



The collateral branches given off by this artery are very numerous, the 

 majority of them being detached from the superior portion of the vessel, near 

 the elbow ; they are intended to supply that articulation, but more especially the 

 muscular masses lying in its neighbourhood, or covering it. 



Such is the usual disposition of the anterior radial artery ; though it is liable 

 to numerous variations — principally in the manner in which it comports itself 

 with the interosseous artery of the forearm, which may even supplement it for 

 the whole of the middle and lower part of its course. This will be noted in 

 describing the next artery. 



2. Posterior Radial Artery (Fig. 377, 1). 



This vessel, in its volume and direction, represents the continuation of the 

 humeral artery. It descends, along with the ulno-plantar nerve, on the internal 

 ligament of the humero-radial articulation, behind the terminal extremity of the 

 biceps ; then under the internal flexor of the metacarpus, its satellite muscle. 

 Arriving at the inferior extremity of the radius, it divides into two terminal 

 branches -, these are the common trunk of the interosseous metacarpal arteries, and 

 the collateral (large metacarpal) artery of the cannon. 



The following are the principal collateral branches furnished by the posterior 

 radial artery : — 



1. At the superior extremity of the radius, articular ramuscules which anasto- 

 mose with analogous branches from the ulnar artery. 



2. A little lower, large divisions destined for the muscles of the posterior 

 antibrachial region, some of them arising from the next artery. 



3. The interosseous artery of the forearm, a considerable vessel which arises at 

 the same point as the preceding — the radio-ulnar arch, and crosses this from 

 within to without, after traversing the posterior face of the radius, beneath the 

 perforans muscle, to descend along the extensor suffraginis, in the channel 

 formed outwardly by the union of the two bones of the forearm. This inter- 

 osseous artery furnishes, immediately after its exit from the radio-ulnar arch, 

 several branches to the articulation of the elbow and the antibrachial muscles. 

 At its terminal extremity it usually divides into a number of branches, the 

 majority of which join the branches sent to the carpus by the anterior radial 

 artery. It is rare that it does show some fine anastomoses with one of the 

 divisions of the latter artery in front of, or outside the articulation of the 

 elbow ; sometimes it directly joins that vessel ; and we have seen it, on the con- 

 trary, receive the anterior radial artery, which it in part supplanted. 



4. Several muscular and musculo-cutaneous ramuscules without any fixed 

 arrangement, arising from different points of the course of the parent artery, 

 below the preceding divisions. 



5. A deep branch, also liable to very numerous variations, having its origin 

 at the radial insertion of the perforatus muscle, descending on the posterior face 

 of the radius, chiefly destined to the carpus, and remarkable for the anastomoses 



