266 DISSECTION OF THE FRONT OF THE FOREARM. 



deep and partly superficial, but where it is more superficial in the lower 

 half it can be felt beating as the pulse near the wrist during life. 



In its upper half l\\e vessel is placed beneath the supinator longus ( 8 ) ; 

 and rests successively on the following muscles, the fleshy supinator brevis, 

 the pronator teres ( 3 ), part of the thin origin of the flexor sublimis ( 6 ), and 

 sometimes on the biceps tendon ( 9 ). 



Veins. Venae comites lie on the sides, with cross branches over the 

 artery. 



Nerve. The radial nerve is parallel to, and outside it, but separated by 

 a slight interval. 



In its lower halfihe artery with its venae comites is superficial, being 

 covered only by the teguments and the deep fascia. Here it is placed in 

 a hollow between the tendons of the supinator longus ( 8 ) and flexor carpi 

 radicalis ( 4 ). It lies from above down on the origin of the flexor sublimis, 

 on two other muscles of the deep layer, viz., flexor pollicis longus and 

 pronator quadratus, and lastly on the end of the radius. 



Nerves. The radial nerve is still on the outer side until it passes back- 

 wards beneath the tendon of the supinator longus, and becomes cutaneous. 

 Superficial to the lower end are the ramifications of the muscnlo-cutaneous 

 nerve, some of which reach the vessels (p. 262). 



Branches. The radial artery furnishes many unnamed muscular and 

 nutrient offsets to the surrounding parts; and three named branches, viz., 

 recurrent radial, superficial volar, and anterior carpal. 



a. The radical recurrent is the first branch, and supplies the muscles 

 of the outer side of the limb. Its course is almost transverse to the supi- 

 nator longus, beneath which it terminates in that muscle and the two 

 radial extensors of the wrist. One offset ascends beneath the supinator, 

 and anastomoses with the superior profunda branch of the brachial artery. 



b. The superficial volar branch (fig. 83, c) arises usually near the lower 

 end of the radius. It is directed towards the palm of the hand, across or 

 through the mass of muscles in the ball of the thumb, and it either ends in 

 those muscles, or joins the superficial palmar arch. 



c. The anterior carpal branch is very inconsiderable in size, and will 

 be seen in the examination of the deep layer of muscles. Arising rather 

 above the end of the radius, it passes transversely at the lower border of 

 the pronator quadratus, and anastomoses with a similar branch from the 

 ulnar artery : from the arch thus formed, offsets are given to the corpus. 



Peculiarities of the radial artery. When the radial arises high in the arm, its 

 course is close to the bracliial artery, along the edge of the biceps muscle ; and in 

 passing the bend of the elbow it may be occasionally subcutaneous, viz., above 

 the deep fascia, and be liable to injury in venesection. In the forearm it may be 

 likewise subcutaneous and superficial to the supiuator loiigus muscle. 



Dissection. To bring ii^to view the flexor sublimis digitorum, the flexor 

 carpi radialis and palmaris.longus must be cut through near the inner con- 

 dyle of the humerus, and turned to one side. Small branches of the ulnar 

 artery and median nerve may be seen entering the under surfaces of those 

 muscles. For the present, the pronator teres may be left uncut. 



The FLEXOR DIGITORUM SUBLIMIS vel PERFORATUS (fig. 80, 6 ) is the 



largest of the muscles of the superficial layer, and is named from its posi- 

 tion to another flexor in the deep layer. It arises from the inner condyle 

 of the humerus and the internal lateral ligament, and from the intermus- 

 cular septa in common with other muscles ; it takes origin in addition from 

 X 





