CHAPTER V. 

 i 



THE ARM. 



ANATOMY. OPERATIONS. 



LANDMARKS. FRACTURES. 



Anatomy. The nerves supplying the superficial fas- 

 cia and integument of the arm are the following : on the 

 inner side of the biceps, the internal cutaneous ; more 

 internally, the intercosto-humeral and the nerve of Wris- 

 berg, while on the outer and posterior aspects are the 

 cutaneous branches of the circumflex and musculo-spiral 

 nerves. Beneath the superficial is the deep fascia which 

 receives expansions from the pectoralis major and latiss. 

 dorsi on the inside, and from the deltoid on the outside. 

 This fascia is thin over the biceps, thicker over the inner 

 aspect of the arm, thickest over the triceps posteriorly, 

 and surrounds the individual muscles forming sheaths for 

 them. The deep fascia separates the muscles on the 

 anterior from those on the posterior surface by means of 

 two septa called trie intermuscular septa external and 

 internal. The former is attached to the external condy- 

 loid ridge and extends from the insertion of the deltoid 

 above to the external condyle below ; the latter to the in- 

 ternal condyloid ridge from the insertion of the coraco- 

 brachialis above to the internal condyle below. The ex- 

 ternal septum is pierced by the musculo-spiral nerve and 

 superior profunda artery about two inches above the ex- 

 ternal condyle, and the internal by the inferior profunda 

 artery and ulnar nerve, a little below the middle of the 

 arm, and by the anastomotica magna about two inches 

 above the internal condyle. By means of these openings 

 the. closed spaces of the posterior communicate with 

 those of the anterior surface of the arm. 



