DISSECTION OF THE ANTERIOR LIMB. 17 



and, disappearing from view, runs upwards at the posterior border of 

 the scapula. It gives off as its most important branches : — 



1. A Muscular branch of considerable volume which passes back wards 

 and upwards on the deep face of the latissimus dorsi. 



2. The Posterior circumflex artery, which turns round behind the 

 shoulder, passing through a triangular space bounded by the teres 

 major, caput magnum, and scapulo-humeralis gracilis. At the outer 

 side of the joint (Plate 7) it appears between the caput magnum, caput 

 medium, and teres minor, and is covered by the deltoid. It splits into 

 branches which are distributed to these muscles and the infraspinatus 

 (Plate 7). It is accompanied by the circumflex nerve. 



3. Other branches of the subscapular are as follows : — A few inches 

 above the origin of the posterior circumflex a vessel is detached which 

 passes backwards, and divides to supply the caput magnum. A number 

 of smaller branches come off from the anterior aspect of the vessel, and 

 are distributed on both surfaces of the scapula. One of these supplies 

 the nutrient artery of the scapula. 



The Scapulo-humeralis Gracilis is a very slender muscle. It arises 

 from the scapula above the rim of its glenoid cavity ; and, passing over 

 the capsular ligament of the shoulder, on which some of its fibres seem 

 to terminate, it insinuates itself between the fibres of the brachialis 

 anticus (humeralis externus), and is inserted into the posterior surface 

 of the shaft of the humerus. It is supplied by a small nerve from the 

 circumflex. 



Action. — The muscle is too inconsiderable in size to exercise any 

 appreciable action on the joint over which it passes, but perhaps 

 it raises the capsular ligament and prevents its injury during flexion 

 of the joint. 



OUTER ASPECT OF THE SHOULDER AND ARM. 







Directions. — The limb is now to be turned over, and the muscles and 

 other structures on the outer side of the scapula and humerus are to be 

 dissected. 



Scapular Fascia. — This is a strong, glistening, fibrous covering which 

 is spread over the muscles on the dorsum of the scapula, affording by 

 its inner surface an origin to many of their fibres. When traced 

 upwards it is seen to be inserted into the scapula or its cartilage of 

 prolongation ; while before, behind, and inferiorly it becomes less 

 fibrous, and is continuous with the fascia covering the muscles on the 

 inner surface of the scapula and the outer aspect of the arm. It 

 furnishes septa to pass between the subjacent muscles, and it is 

 adherent to the tubercle on the scapular spine. If an attempt be 

 made to dissect it off these muscles they will be exposed with a 



c 



