THE BRACHIAL OR AXILLARY ARTERIES. 567 



These terminal ramuscules of the anterior radial artery are distributed 

 to tJhe carpal articulation, or the sheaths of the extensor tendons, and com- 

 municate 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 fore-arm, which may even supple- 

 ment 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. (Figs. 283, 1 ; 347, B.) 



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 coraco-radialis ; then under the internal flexor of the meta- 

 carpus, its satellite muscle. Arriving at the inferior extremity of the radius, 

 it divides into two terminal branches ; which are, the common trunk of the 

 interosseous metacarpal arteries and the collateral 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 

 anastomose with analogous branches from the epicondyloid 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 fore-arm, a considerable vessel which 

 originates at the same point as the preceding the radio-ulnar arch, and 

 which crosses this from within to without, after traversing the posterior face 

 of the radius, beneath the perforans muscle, to descend along the lateral 

 extensor muscle of the phalanges, in the channel formed outwardly by the 

 union of the two bones of the fore-arm. This interosseous 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 ; some- 

 times it directly joins that vessel ; and I have seen it, on the contrary, 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 that its internal divisions contract with the anterior 

 radial artery, and for those which occasionally unite its external ramifications 

 to the ultimate branches of the interosseous artery of the fore-arm or the 

 epicondyloid artery (Fig. 283, 2). 



