THE UPPER LIMB 4^7 



posterior interosseous, are to be shown. In this part of its course the nerve 

 will be found to furnish branches to the brachio-radialis and extensor carpi 

 radiaUs longior, and a twig to the brachiaUs anticus, the latter arising high 

 up in the spiral groove. Descending with the musculo-spiral nerve in this 

 groove will be found the anterior terminal branch of the superior profunda 

 artery, and coming up from below to anastomose with it a branch of the radial 

 recurrent. 



The anticubital space or triangular hollow in front of the elbow is next 

 to be dissected, and its roof, floor, boundaries, and contents carefully studied. 

 If the brachio-radialis is held aside, the posterior interosseous nerve will 

 be seen piercing the supinator radii brevis ; and, if the superficial head of 

 the pronator radii teres is raised, the anterior ulnar recurrent artery, of 

 small size, will be found ascending to the front of the internal epicondyle, 

 where it anastomoses with the anterior branch of the anastomotica magna. 

 The mode of insertion of the tendon of the biceps is to be carefully noted, and 

 its action in this connection studied. 



Back of the Brachial Region. — The triceps is to be dissected, and its three 

 heads clearly shown. The long head is obvious, but the external and internal 

 heads require careful dissection. The dissector should pull upon the musculo- 

 spiral nerve to make evident its winding course round the back of the humerus, 

 and he should then make an incision through the muscle over the course of 

 the nerve, avoiding its long head. When the cut parts of the muscle are 

 separated, the spiral groove of the humerus is laid bare, with the musculo- 

 spiral nerve and superior profunda artery lying in it. The portion of the 

 muscle above and external to the groove is the external head, and the small, 

 peaked portion inside the groove and all the fibres arising from the back of 

 the humerus below the groove represent the internal head. 



The branches of the musculo-spiral nerve behind the humerus are to be 

 shown, and one long branch to the anconeus, which descends in the internal 

 head of the triceps, is to be followed out. The nerve, on leaving the spiral 

 groove, will be seen to pierce the external intermuscular septum from behind 

 forsvards, along with the anterior branch of the superior profunda artery. This 

 artery is also to be dissected, and its posterior terminal branch is to be shown 

 descending behind the external intermuscular septum to the back of the 

 external epicondyle, where it anastomoses with the posterior interosseous 

 recurrent. The internal head of the triceps may now be cut into interiorly, 

 in order to show its deepest fibres, under the name of the subanconeus, taking 

 insertion into the back part of the capsule of the elbow- joint. 



Acromio-clavicuiar Joint. — In connection with this joint the coraco- 

 clavicular Ugament is to be displayed in two parts — conoid and trapezoid — 

 and between these will be found a little fat and a small bursa. The ligaments 

 of the joint itself are next to be dissected, and, when the joint is opened, an 

 incomplete interarticular libro-cartilage may be found within it at the upper 

 part. 



Special Ligaments of the Scapula. — The suprascapular or transverse Ugament 

 is to be made evident, with the suprascapular nerve passing backwards 

 beneath it, the suprascapular artery over it, and fibres of the posterior belly of 

 the omohyoid arisii^ from it. The coraco-acromial or deltoid hgament is 

 next to be dissected, and its relation to the capsule of the shoulder-joint care- 

 fully noted. The spino-glenoid hgament is to be shown passing between the 

 outer border of the spine and the adjacent part of the margin of the glenoid 

 cavity. It will be seen to bridge over the suprascapular artery' and nerve on 

 their way to the infraspinous fossa. 



Shotllder-Joint. — The dissector should first revise the subacromial bursa 

 and the muscular relations of the capsule of this joint. The capsular Ugament 

 is then to be studied, and the coraco-humeral hgament is to be noted incor- 

 porated with its upper aspect. Two openings in the capsule are to be 

 observed. One is situated in front, behind the upper border of the tendon 

 of the subscapularis, and through this opening the sjTiovial membrane wiU 

 be found protruding to form the subscapular bursa. The other opening is 

 situated between the tuberosities of the humerus, at the entrance to the bi- 



27 



