RADIAL AND ULNAR ARTERIES. 



225 



the palm from the forcibly extended thumb 

 might be taken as a more accurate guide to 

 this part of the vessel. 



Branches of the ulnar artery. The first 

 branches of the vessel are two, which usually 

 come off by a common trunk, but are nearly 

 as often separate at their origin. They are 

 called the arteries recurrentes ulnares anterior 

 et posterior, being so named from their taking 

 a recurved course upwards into the arm ; the 

 former in the front of the internal condyle of 

 the humerus, and the latter between it and 

 the olecranon process of the ulna. The an- 

 terior recurrent passes upwards from beneath 

 the flexor muscles which cover the artery 

 where it rises, lying on the brachialis anticus, 

 and corresponding to the elbow joint which 

 it partially supplies ; its superior termination 

 inosculates with the lowest or anastomotic 

 branch of the brachial. The posterior re- 

 current, having at first similar relations, passes 

 more inwards so as to reach the above in- 

 terval, being situated beneath the flexor carpi 

 ulnaris, and meeting the ulnar nerve de- 

 scending from the arm between the two heads 

 of this muscle. Here it breaks up, anasto- 

 mosing freely with the inferior profunda which 

 has hitherto accompanied the nerve, uniting 

 also by small branches with twigs sent down- 

 wards from the superior profunda in the 

 substance of the triceps, and giving many 

 branches to the articulation and the neigh- 

 bouring muscles. 



The next considerable branch is the arteria 

 interossea, which diverges from the trunk of 

 the vessel a little below the coronoid pro- 

 cess, and whilst it is covered by the flexor 

 muscles. Directed downwards from its 

 origin, after a course of about an inch in 

 length, it reaches the interosseous mem- 

 brane in the upper part of the interval 

 between the flexor longus pollicis and the 

 flexor profundus digitorum, and here it bi- 

 furcates into two branches. One of these, 

 the anterior interosseous, continues on the 

 front of this membrane, lying deeply in the 

 interval between the two 'muscles and con- 

 cealed by them, until, arriving at the pro- 

 nator quadratus which lies transversely across 

 the lower extremities of the radius and ulna, 

 it passes under this muscle. At its inferior 

 border it reappears, though much diminished 

 in size, and now situated on the anterior 

 ligament of the wrist, it divides into many 

 small branches, which supply the articulation 

 and anastomose with the anterior carpal twigs 

 from the radial and ulnar vessels. In this 

 course, the branch now described supplies 

 the muscle on each side of it, and usually it 

 gives off one or two small branches which 

 perforate the interosseous membrane beneath 

 it in their passage backwards to the posterior 

 region of the forearm. One of these, by far 

 the largest and the most constant, is fre- 

 quently named as " the posterior branch of 

 the anterior interosseous;" and it escapes 

 to the back of the forearm, through an aper- 

 ture which exists in the interosseous mem- 

 brane, near its inferior border, and about an 



VOL. IV. 



inch and a half above the radio-ulnar articu- 

 lation. 



The posterior interosseous, the remaining 

 division of the artery, leaves the front of the 

 limb by passing between the radius and ulna 

 above the superior border of the interosseous 

 membrane, and next becomes visible in the 

 back of the forearm, between the inferior 

 border of the supinator brevis and the ex- 

 tensor ossis metacarpi pollicis. In the re- 

 mainder of its extent it lies on the muscles 

 which arise from the posterior surface of this 

 membrane, and beneath the more superficial 

 layer of extensors and supinators, until it 

 arrives at the wrist. Here, lying on the pos- 

 terior ligament of the joint, it breaks up into 

 its terminal ramifications, which inosculate 

 freely with the posterior carpal arteries of 

 the radial and ulnar, and with the perforating 

 branch of the anterior interosseous division. 



While this vessel is passing between the 

 two bones above the ligament, it gives off the 

 recurrent interosseous branch, which, usually 

 of considerable size, perforates the lower part 

 of the supinator radii brevis to reach the 

 back of the forearm. Subsequently it is 

 directed upwards, lying on this muscle, and 

 beneath the anconeus, until it attains the 

 lower part of the arm, where it terminates by 

 anastomosing with a large branch or branches 

 which proceed from the superior profunda, as 

 it turns round the humerus, and in the sub- 

 stance of the outer head of the triceps. It 

 supplies the muscles between which it is 

 situated, and sends a branch to the articula- 

 tion of the elbow-joint. 



A very constant branch, though usually only 

 of small size, is the twig from the ulnar artery 

 which accompanies the median nerve, con- 

 tinuing along it through the forearm until 

 gradually lost from increasing minuteness. It 

 is the basis of an important variety which 

 will be mentioned hereafter. 



Low down in the forearm, the ulnar artery 

 gives off a branch which runs along the ulnar 

 side of the metacarpus, and supplies this side 

 of the little finger with a dorsal twig. Ac- 

 companied by a branch of the ulnar nerve, it 

 turns backwards from the vessel just above 

 the inferior extremity of the ulna, beneath 

 the flexor carpi ulnaris tendon ; and reaching 

 the inner side of the wrist, continues in a 

 direct line to its termination. It anastomoses 

 with the posterior carpal arch, and, on the 

 metacarpus, with the palmar arch of the 

 ulnar artery. 



The remaining branches of the ulnar in the 

 forearm are two, the arteries carpi ulnares 

 anterior et posterior, which occupy a position 

 closely resembling that of the similar branches 

 from the radial artery on the opposite side of 

 the limb. Each runs transversely outwards 

 on its respective surface of the wrist joint, 

 and unites with the radial branch, and from 

 this union, (which, in the case of the posterior 

 vessels, is a " carpal arch" in size and re- 

 gularity of arrangement) branches perforate 

 the ligaments to supply the articulations and 

 bones of the carpus. In addition to the 



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