THE BRACHIAL PLEXUS 



1041 



Circumflex. 



supply the outer and inner heads of the Triceps and Anconeus muscles. The 

 branch for the latter muscle is a long, slender filament which descends in the 

 substance of the Triceps to the Anconeus. The external muscular branches supply 

 the Brachioradialis, Extensor 

 carpi radialis longior, and 

 (usually) the outer part of the 

 Brachialis anticus muscles. 



The cutaneous branches are 

 three in number, one internal 

 and two external. The inter- 

 nal cutaneous branch (n. cuta- 

 ueus brachii posterior) arises 

 in the axillary space with. the 

 inner muscular branch. It is 

 of small size, and passes 

 through the axilla to the inner 

 side of the arm, supplying the 

 integument on its posterior 

 aspect nearly as far as the 

 olecranon. In its course it 

 crosses beneath the intercosto- 

 humeral nerve, with which it 

 communicates. The external 

 cutaneous branch (n. cutaneus 

 atttebrachii dorsal is) divides 

 into two branches, and each 

 one perforates the outer head 

 of the Triceps muscle at its 

 attachment to the humerus. 

 The upper and smaller one 

 passes to the front of the 

 elbow, lying close to the 

 cephalic vein, and supplies the 

 integument of the lower half of 

 the arm on its anterior aspect. 

 The lower branch pierces the 

 deep fascia below the insertion 

 of the Deltoid muscle, and 

 passes down along the outer 

 side of the arm and elbow, 

 and then along the back part 

 of the radial side of the fore- 

 arm to the wrist, supplying 

 the integument in its course, 

 and joining, near its termi- 

 nation, with the posterior 

 cutaneous branch of the mus- 

 culocutaneous nerve. 



The Radial Nerve (ramus superficial n. radialis) (Fig. 764), passes along the 

 front of the radial side of the forearm to the commencement of its lower third. 

 It lies at first a little to the outer side of the radial artery, concealed beneath the 

 Brachioradialis. In the middle third of the forearm it lies beneath the same 

 muscle, in close relation with the outer side of the artery. It leaves the artery 

 about three inches above the wrist, passes beneath the tendon of the Brachio- 



66 



FIG. 765. The suprascapular, circumflex, and musculospiral 

 nerves. 



