488 ARTERIES. 



palmar arch. At its termination, it inosculates with the deep branch of the 

 ulnar artery. The relations of this vessel may thus be conveniently divided 

 into three parts, viz., in front of the forearm, at the back of the wrist, and in 

 the hand. 



Relations. In the forearm, this vessel extends from opposite the neck of the 

 radius, to the fore-part of the styloid process, being placed to the inner side of 

 the shaft of the bone, above, and in front of it below. It is superficial throughout 

 its entire extent, being covered by the integument, the superficial and deep fascia, 

 and slightly overlapped above by the Supinator Longus. In its course down- 

 wards, it lies upon the tendon of the Biceps, the Supinator Brevis, the Pronator 

 Eadii Teres, the radial origin of the Flexor Sublirnis Digitorum, the Flexor 

 Longus Pollicis, the Pronator Quadratus, and the lower extremity of the radius. 

 In the upper third of its course, it lies between the Supinator Longus and the 

 P.ronator Eadii Teres ; in its lower two-thirds, between the tendons of the 

 Supinator Longus and the Flexor Carpi Eadialis. The radial nerve lies along 

 the outer side of the artery, in the middle third of its course; and some fila- 

 ments of the musculo-cutaneous nerve, after piercing the deep fascia, run along 

 the lower part of the artery as it winds round the wrist. The vessel is accom- 

 panied by vense comites throughout its whole course. 



PLAN OF THE EELATIONS OF THE EADIAL ARTERY IN THE FOREARM. 



In front. 



Integument superficial and deep fasciae. 

 Supinator Longus. 



Inner side. f R a dj a i \ Outer side. 



Pronator Radii Teres. ( Artery in ) Snpinator Longus. 



Flexor Carpi Badialis. \ Forearm. 1 Radial nerve (middle third). 



Behind. 



Tendon of Biceps. 

 Supinator Brevis. 

 Pronator Radii Teres. 

 Flexor Sublimis Bigitorum. 

 Flexor Longus Pollicis. 

 Pronator Quadratus. 

 Radius. 



At the ivrist, as it winds round the outer side of the carpus, from the styloid 

 process to the first interosseous space, it lies upon the external lateral ligament, 

 being covered by the extensor tendons of the thumb, subcutaneous veins, some 

 filaments of the radial nerve, and the integument. It is accompanied by two 

 veins, and a filament of the musculo-cutaneous nerve. 



In the hand, it passes from the upper end of the first interosseous space, be- 

 tween the heads of the Abductor Indicis or first Dorsal Interosseous muscle 

 transversely across the palm, to the base of the metacarpal bone of the little 

 finger, where it inosculates with the communicating branch from the ulnar 

 artery, forming the deep palmar arch. It lies upon the carpal extremities of 

 the metacarpal bones and the Interossei muscles, being covered by the flexor 

 tendons of the fingers, the Lumbricales, the muscles of the little finger, and 

 the Flexor Brevis Pollicis, and is accompanied by the deep branch of the ulnar 

 nerve. 



Peculiarities. The origin of the radial artery varies in the proportion nearly of one in eight 

 cases. In one case the origin was lower than usual. In the other cases, the upper part of the 

 brachial was a more frequent source of origin than the axillary. The variations in the position 

 of this vessel in the arm, and at the bend of the elbow, have been already mentioned. In the 

 forearm it deviates less frequently from its position than the ulnar. It has been found lying 

 over the fascia, instead of beneath it. It has also been observed on the surface of the Supina- 

 tor Longus. instead of along its inner border: and in turning round the wrist, it has been seen 

 lying over, instead of beneath, the extensor tendons. 



