ANATOMY OF THE ANTHROPOID APES. 187 



the scapular ligament, and partly on to the head of the humerus, but chiefly on to 

 the greater tuberosity, and just below the insertion of the infraspinatus. 



(17) Infraspinatus. — This muscle covers over the whole of the infraspinous fossa. 

 It does not, however, arise from the middle of the fossa, only from the spine and from 

 the lower border, except posteriorly ; it also arises from the septa between itself and the 

 following muscles : deltoid, teres major, teres minor. It is largely tendinous at its 

 insertion: the tendon arises first just within the muscle, but subsequently reaches the 

 lower surface ; it is inserted partly on to the capsular ligament of the humerus, and 

 partly on to the humerus itself. 



(IS) Supraspinatus. — This muscle, unlike the infraspinatus, arises from the greater 

 part of the supraspinous fossa; its tendon of attachment first commences within the 

 substance of the muscle. 



(19) Subscapularis. — This muscle is covered below (on the fr-se surface) by a strong 

 aponeurosis, from which its fibres partly arise ; this fascia has a specially strong 

 attachment to the lower angle of the scapula. The muscle arises from the greater 

 part of the subscapular fossa. 



(20) Triceps. — This muscle has the usual three heads (not reckoning the dorso- 

 epitrochlear, which has been already described in connection with the latissimus dorsi) ; 

 the scapular head is largely tendinous on the lower surface ; the tendinous aponeurosis 

 gradually diminishes in extent, and terminates just after the junction of the scapular 

 and humeral heads of the muscle. The scapular head arises chiefly from the lower 

 border of the scapula along a line measuring two and a half inches in length ; the 

 origin is partially from the septa between itself and the teres major, teres minor, 

 and subscapularis. The origin of the outer humeral head commences just below the 

 head of the humerus ; the inner humeral head commences much lower down ; anteriorly 

 some of its fibres arise in common with those of the outer humeral head ; further back 

 the origins of the two heads are quite distinct. Both humeral heads arise not only 

 from the humerus, but also from the septa between themselves and adjacent muscles. 



(21) Srachialis anticus. — The origin of this muscle commences just below the 

 deltoid. 



(22) Supinator radii longus arises just in front of the supinator carpi radialis longior 

 from the humerus ; it also takes origin from the septa between itself and the triceps, 

 the hracliialis anticus, and the supinator ; the line of origin measures two and a half 

 inches ; it is inserted by a broad flat tendon two and a half inches in length. 



(23) JExtensor carpi radialis longior is the most external of the extensor muscles of 

 the hand ; it arises chiefly from the lower part of the external condylar ridge of the 

 humerus just below the last muscle, and from the external condyle itself in common 

 with the extensor carpi radialis brevior. The muscle is short, not reaching halfway 

 down the forearm ; the long tendon passing under the tendon of the extensors of the 

 thumb is inserted on to the inner side of the base of the second metacarpal. 



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