M. CORA COIDEUS. 251 



Posture. The brachium forms nearly a, right angle with both 

 the scapula and the antebrachium. Place the arm upon its cephalic 

 surface, let the antebrachium and manus rest against the rim of the 

 tray toward the dissector, and place a block flatwise under the 

 scapula and shoulder so that the brachium forms an angle of about 

 45 degrees with the tray. 



Exposure. Remove the fascia, fat, connective tissue, vessels 

 and nerves upon the caudal aspect of the shoulder and brachium. 

 In doing this, watch very carefully for the slender tendon (of the 

 caput longum, Fig. 75), which extends, in some cases, nearly the 

 whole length of the brachium ; use the tracer more than the knife, 

 and remove nothing until sure that the tendon is not included. 



General Description. This muscle consists of two parts (caput 

 longum and cp. breve), so distinct that, if they were larger, they 

 probably would be regarded as two muscles ( 573). They arise 

 from the coracoid process of the scapula and are inserted into the 

 Jmmerus near its proximal and distal ends. Both parts are so 

 small as to be easily overlooked. 



Dissection. Feel for the coracoid process in the triangular inter- 

 val at the head of the humerus between the distal ends of the sub- 

 scapularis and supraspinatus (Fig 73, 75) ; the tip of the process 

 is just at the border of the former muscle near the apex of the inter- 

 val. Carefully lift the border of the subscapularis with the forceps, 

 and use the tracer and scalpel to dissect between it and the slender 

 coracoideus. The latter lies upon the capsule of the joint and 

 sometimes adheres quite firmly to it. 



Separate the connections, when they exist, with the tracer, and 

 divide the muscle so as to follow the course of the shorter and more 

 fleshy part (caput breve) from the coracoid process to the surgical 

 neck of the humerus. The dissection of the longer and more slen- 

 der caput longum should be done almost wholly with the tracer, 

 and the delicate tendon should not be pulled in tracing it toward 

 the distal end of the humerus. 



669. Origin. The common origin of the two heads from the 

 tip of the coracoid process is by a tendon about 1 mm. long. 



Insertion. The short head is inserted by fleshy fibers upon the 

 caudal surface of the surgical neck of the humerus ; the length of 

 the area of insertion is approximately equal to half the distance 

 from its proximal end to the proximal end of the humerus, and the 

 width equals half the length. The ventral margin of the area of its 



