Warren Harmon Lewis 173 



Tlic infraspinatus nniscle arises from the anterior portion of the 

 lateral sin-face of the scapula and can bo easily traced to its insertion 

 into the great tuberosity of the humerus. The teres minor cannot be 

 separated from it. 



The supraspinal us muscle arises from the anterior thickened border 

 of the scapula and passes to the great tuberosity of the humerus. 



The suhscapularis muscle occupies the central portion of the median 

 surface of the scapula. It is separated from the teres major. It passes 

 beneath coracoid process to the lesser tuberosity of the humerus. 



The triceps muscle is easily traced from its origin by the three heads 

 to its insertion into the olecranon process. The three heads are quite 

 easily distinguished. The long head is smaller in proportion than in the 

 adult. 



The biceps muscle is more elongated and shows more of a separation 

 of its two heads than in embryo CIX. The long head still arises from 

 the base of the coracoid process. The two heads join about the middle 

 of the humerus and pass to a thickening of condensed tissue on the 

 radius. The short head arises in common with the coracobrachialis mus- 

 cle from the tip of the coracoid process. This latter muscle is inserted 

 into the middle of the median surface of the humerus. It is closely 

 connected with the biceps for most of its length. 



The hracJiiaUs muscle is spread out more over the distal portion of the 

 humerus and its muscle fibers extend farther toward the insertion into 

 the coronoid process of the ulna than in the preceding stage. 



The fte.ror mass of the forearm and hand show a most marked ad- 

 vance over the preceding stage. The various muscles of the superficial 

 layer which arise from the internal condyle are easily recognized. They 

 are more or less fused at their origin and for some little distance from it. 



The pahnaris longus muscle, the most superficial one, is thin and 

 wide, ends in the condensed tissue of the palmar fascia. 



The pronator teres muscle passes to the middle of the shaft of the 

 radius. 



The flexor carpi radialis muscle lies mostly on the radial side of the 

 forearm, towards the distal end of which it bends under the deep flexor 

 and ends in a condensed tissue tendon which fuses with the condensed 

 tissue near the proximal end of the second metacarpal. This portion 

 of the muscle is not yet clearly differentiated from the condensed tissue 

 on the palmar surface of the caqms. 



The flexor digitonim suhlimis muscle arises beneath the palmaris 

 longus in connection with it from the internal condyle, and also from 

 the shaft of tlie ulna, for a little distance distal of the coronoid ]~)rocess. 



