SUPEKFICIAL PALMAR ARCH. 411 



the high ulnar separates is afterwards divided into the radial artery and the 

 interosseous, the last of which is usually derived from the ulnar ; it appears 

 therefore probable that the abnormal an-angement results from early obstmction 

 of the ulnar artery below the origin of the interosseous, and the development of 

 a superficial vas aberrans, which unites the portion of vessel below the obstruc- 

 tion with the axillary or brachial trunk. The interosseous artery in such cases of 

 abnoiTaality thus comprises not only the ordinary interosseous branch, Ijut like- 

 wise the portion of ulnar artery above the obstruction ; and, in accordance with 

 this view, we find that the recurrent branches are derived from it. 



As to size, the ulnar artery presents some peculiarities which, being accom- 

 panied by deviations of an opposite and compensating character in the radial 

 artery, will be noticed with that vessel. 



Branchca. — The anterior and jjo-sterior ttlnar recurrent hrancliex frequently arise 

 by a common trunk. One or both have been seen to arise from the brachial 

 artery. 



The anterior and poster iar interosseous arteries are occasionally given separately 

 from the ulnar. The common interosseous trunk has been found to arise above 

 its ordinary situation, taking origin from the brachial, and even (but more 

 rarely) from the axillary artery. The anterior interosseous presents some striking 

 varieties of excess in its branches, usually connected with a deficiency in the 

 radial or ulnar arteries : the most important of these is enlargement of the 

 median branch. 



Median artery. — The branch accompanying the median nerve is sometimes 

 much enlarged, and in such cases may be regarded as a reinforcing vessel. It is 

 generally a branch of the anterior interosseous, but sometimes of the ulnar ; and 

 more rarely a median branch has been met with descending from the Ijrachial 

 artery. Accompanying the median nerve beneath the annular ligament into the 

 palm of the hand, the median artery ends most frequently by joining the super- 

 ficial palmar arch, sometimes by forming digital branches, in otlier case? by 

 joining digital branches given from other soui'ces. 



SUPEKFICIAL PALMAR AECH. 



The superficial palmar arch or artery is the continuation of the ulnar 

 nrtery into the hand. Changini^ its course near the lower border of 

 the annular ligament, this artery turns obliquely outwards across the 

 palm of the hand towards the middle of the muscles of the thumb, 

 ^vhere it terminates by inosculating with the superficial volar branch of 

 the radial artery. In its course across the hand, the palmar artery 

 describes a curve, having its convexity directed towards the lingers, 

 and extending downwards somewhat lower than a line on a level with 

 the phalangeal articulation of the thumb. 



The superficial palmar artery rests at its commencement on the 

 annular ligament of the wrist, and slightly on the short muscles of the 

 little finger ; then on the tendons of the superficial flexor of the fingers, 

 and the divisions of the median and ulnar nerves, the latter nerve 

 accompanying the vessel for a short distance. It is covered towards (he 

 ulnar border of the hand by the palmaris brevis, and afterwards by the 

 palmar fascia and the integument. 



Branches. — Tlie branches given off by the superficial palmar arch, 

 which are generally numerous, are as follow. 



{a) The deep or coiiimnmcatmg branch arises from the rJnar artery 

 at the commencement of the palmar arch a little beyond the pisiform 

 bone, sinks deeply between the flexor brevis and the abductor of the little 

 finger, and inosculates with the palmar termination of the radial artery, 

 thereby completing the deep palmar arch. 



(b) Small rscurrent branches, followinsj a retrograde course towards 



