TRICEPS EXTENSOR OF MUSCLE. 



257 



the forearm (supinator longus and extensor carpi radialis longior), which 

 extend upwards on the humerus. 



Action. The brachialis brings forwards the ulna towards the humerus, 

 and bends the elbow-joint. 



If the ulna is fixed, as in climbing with the hands above the head, the 

 muscle bends the elbow-joint by raising the humerus. 



BACK OF THE ARM. 



Position. During the examination of the back of the arm, the limb is 

 to be raised in a semiflexed position by means of a block beneath the elbow. 

 The scapula is to be brought nearly in a line with the humerus, so as to 

 tighten the muscular fibres ; and it is to be fastened with hooks in that 

 position. 



Muscles : 



A. Long head of the triceps. 



B. Outer head, with a bit of whalebone beneath it 



to mark the extent of its attachment down the 



humerus. 



c. Inner head of the triceps. 

 D. Anconeus- 

 K. Supinator longus. 



F. Extensor carpi radialis longus. 



G. Tercs major. 

 H. Teres miiior. 



I. Infra-spinatus, cut across. 

 J. Supra-spinatus, cut through. 

 Arteries : 

 a. Supra-scapular. 

 &. Dorsal scapular. 

 c. Posterior circumflex. 



Nerves : 



1. Supra-scapular. 



2. Posterior circumflex. 



DISSECTION 



THK DORSAL SCAPULAR VESSELS AXD XERVE, AND OP THE TRICEPS MCSCLE 

 OF THE ARM. 



Dissection (fig. 79). On the back of the arm there is one muscle, the 

 triceps, with the musculo-spiral nerve and superior profunda vessels. The 

 skin having been reflected already, the muscle will be laid bare readily, 

 for it is covered only by fascia. To take away the fascia, carry an inci- 

 sion along the middle of the limb to a little below the elbow ; and in reflect- 

 ing it, the subaponeurotic loose tissue should be removed at the same time. 

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