THE RADIAL ARTERY 647 



space between the metacarpal bones of the thumb and index finger, and finally 

 passes forward, between the two heads of the First dorsal interosseous muscle, 

 into the palm of the hand, where it crosses tne metacarpal bones to the ulnar border 

 of the hand, to form the deep palmar arch. At its termination it anastomoses with 

 the profunda branch of the ulnar artery. The relations of this vessel may thus 

 be conveniently divided into three parts viz., in 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 overlapped in the upper part of its course by the fleshy belly of the 

 Brachioradialis muscle; throughout the rest of its course it is superficial, being covered by the 

 integument, the superficial and deep fasciae. In its course downward it lies upon the tendon 

 of the Biceps, the Supinator [brevis], the Pronator teres, the radial origin of the Flexor sublimis 

 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 Brachioradialis and the Pronator 

 teres; in the lower two-thirds, between the tendons of the Brachioradialis and the Flexor carpi 

 radialis. The radial nerve lies close to the outer side of the artery in the middle third of its 

 course, and some filaments of the musculocutaneous nerve, after piercing the deep fascia, run 

 along the lower part of the artery as it winds around the wrist. The vessel is accompanied by 

 venae comites throughout its whole course. 



PLAN OF THE RELATIONS OF THE RADIAL ARTERY IN THE FOREARM. 



In front. 



Skin, superficial and deep fasciae. 

 Brachioradialis. 



Inner side. / \ Outer side. 



Pronator teres. I j2J / Brachioradialis. 



Flexor carpi radialis. V J Radial nerve (middle third). 



^-^ 



Behind. 



Tendon of Biceps. 



Supinator [brevis]. 



Pronator teres. 



Flexor sublimis digitorum. 



Flexor longus pollicis. 



Pronator quadratus. 



Radius. 



At the wrist, as it winds around the outer side of the carpus from the styloid process to the 

 first interosseous space, it lies upon the external lateral ligament, and then upon the scaphoid 

 bone and trapezium, 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 musculocutaneous nerve. 



In the hand it passes from the upper end of the first interosseous space, between the heads 

 of the Abductor indicis or First dorsal interosseous muscle, transversely accross the palm, to 

 the base of the metacarpal bone of the little finger, where it anastomoses with the communi- 

 cating branch from the ulnar artery, forming the deep palmar arch. 



The deep palmar arch (arcus volaris profundus) (Fig. 464) lies upon the 

 carpal extremities of the metacarpal bones and the Interossei muscles, being 

 covered by the Adductor obliquus pollicis, the Flexor tendons of the fingers, the 

 Lumbricales, the Opponens, and Flexor brevis minimi digiti. Alongside of it, 

 but running in the opposite direction that is to say, from within outward is 



