1 32 THE SUPERIOR EXTREMITY 



branches of the radial nerve, and gives off several twigs for 

 the supply of the muscles arising from the lateral epicondyle 

 of the humerus. Somewhat reduced in size, it now turns 

 proximally, in the interval between the brachio-radialis and 

 brachialis, and ends, in front of the lateral epicondyle of the 

 humerus, by anastomosing with the anterior terminal branch 

 of the profunda brachii artery. It may be represented by 

 two or more vessels. 



The superficial volar artery is a small, variable branch, 

 which arises a short distance proximal to the wrist, and runs 

 distally to end in the muscles of the ball of the thumb. Some- 

 times, however, it attains a larger size and a special importance, 

 because it is continued into the palm to complete the super- 

 ficial volar arch, on the lateral side. 



The volar radial carpal artery is a minute twig which springs 

 from the radial at the distal border of the pronator quadratus 

 muscle. It runs medially, under cover of the flexor tendons, 

 and joins with the corresponding branch of the ulnar artery 

 to form the volar carpal arch. 



The Ramus Superficialis and the Eamus Profundus of 

 the Nervus Radialis (O.T. Radial and Posterior Interos- 

 seous Nerves). It has already been noted that the radial 

 nerve ends proximal to the elbow, under cover of the brachio- 

 radialis muscle, by dividing into two terminal branches, 

 the superficial branch and the deep branch. Both branches 

 may now be studied in so far as they lie in the volar 

 part of the forearm. The ramus profundus soon dis- 

 appears from view by passing backwards, on the lateral 

 side of the radius, through the fibres of the supinator 

 muscle. 



The superficial branch proceeds distally, under cover 

 of the fleshy belly of the brachio-radialis. In the middle 

 third of the forearm it lies along the lateral side of the radial 

 artery ; then it leaves the artery and winds round the lateral 

 margin of the limb, under cover of the tendon of the 

 brachio-radialis. It has been traced in the rest of its 

 course (p. 71). The superficial branch is a purely cutaneous 

 nerve ; and it gives off no branches until it gains the dorsal 

 aspect of the distal part of the forearm. 



Dissection. Before the cleaning of the superficial flexor 

 muscles is commenced an attempt should be made to demonstrate 

 the mucous sheaths of the flexor tendons. They are the common 



