DORSUM OF THE ARM 115 



Dissection. In order that the radial nerve and the profunda 

 brachii artery may be fully exposed, the lateral head of the 

 triceps must be divided. Thrust the handle of a knife along the 

 sulcus for the radial nerve, and under the muscle. The handle 

 will then give the direction in which the lateral head of the 

 triceps should be severed. Beyond cleaning the nerve and its 

 branches, and the profunda brachii artery, as they lie in the 

 groove, no further dissection is necessary. 



Nervus Radialis (O.T. Musculo-Spiral Nerve). The radial 

 nerve is the direct continuation of the posterior cord of the 

 brachial plexus after it has furnished, in the axilla, the two 

 subscapular nerves, the thoraco-dorsal nerve, and the axillary 

 nerve. In the first instance, the radial nerve proceeds distally, 

 behind the distal part of the axillary artery and the proximal 

 part of the brachial artery. It soon leaves the anterior aspect 

 of the arm, however, and, inclining backwards, with the pro- 

 funda brachii artery, enters the interval between the long and 

 the medial heads of the triceps, and reaches the sulcus for the 

 radial nerve. In that it passes round the back of the body of 

 the humerus, under cover of the lateral head of the triceps, and 

 on the lateral side of the limb it pierces the lateral intermuscular 

 septum and passes into the anterior compartment of the arm, 

 where it has already been dissected. There it lies deeply, in 

 the interval between the brachialis on the medial side and 

 the brachio-radialis and extensor carpi radialis longus on the 

 lateral side, and it ends at the level of the lateral epicondyle of 

 the humerus by dividing into two terminal branches, viz., the 

 ramus superficial (O.T. radial) and the ramus profundus 

 (O.T. posterior interosseous). The radial nerve presents, 

 therefore, very different relations as it is traced from its origin 

 to its termination: (i) between the subscapularis, latissimus 

 dorsi, teres major, and long head of the triceps, which support 

 it behind, and the axillary and brachial arteries which are 

 placed in front of it ; (2) between the long and the medial heads 

 of the triceps ; (3) in the sulcus for the radial nerve, between 

 the bone and the lateral head of the triceps ; (4) in the 

 interval between the brachialis on the medial side, and the 

 brachio-radialis and extensor carpi radialis longus on the 

 lateral side. 



The branches which proceed from the radial nerve are 

 muscular, cutaneous, articular and terminal. 



The cutaneous branches are two in number, and have already 

 been traced. They are (i) the posterior cutaneous nerve of 



