THE MUSCLES OF THE UPPER EXTREMITY. 91 



bestowed upon the present muscle, as it seems to com- 

 bine the teres major and the supraspinatus of such 

 vertebrates wherein these muscles are found separate. 

 Even iii old muscular subjects among the Ravens, one 

 is almost led to believe that the two can be fairly dis- 

 tinguished, the division being indicated by a somewhat 

 broader dividing fascia, 



The teres et infraspinatus possesses fully four or 

 five times the bulk of the supraspinatus, and is the 

 largest muscle, by all odds, that is attached to the 

 shoulder-blade (see Figs. 24, 27, and 34). 



It arises from the superior surface and the outer 

 margin of the hinder two- thirds of the scapula, extending 

 in fact between the posterior termination of the supra- 

 spinatus to the apex of the bone. Its fibres rapidly 

 converge as they pass forwards and outwards to their 

 point of insertion upon the corresponding humerus. 

 This is found upon the anconal surface of that bone 

 at about the middle of the free ulnar margin, of the 



O 



pneumatic fossa ; the external head of the triceps 

 forking to allow this muscle room to attach itself 

 (Fig. 27). 



Owen says in the Apteryx that it " is inserted into 

 the ulnar tuberosity of the humerus, where it is closely 

 attached to the capsule of the shoulder-joint." 



The major portion of both of these last-described 

 muscles lie beneath the latissimus dorsi, the supra- 

 spinatus being the less covered of the two (Fig. 33). 



Chief among the uses of these muscles is the protection 

 they afford the shoulder-joint, and acting as braces 

 they greatly assist keeping the humerus in its shallow 

 socket. After the wing has been extended, they, by 

 their contraction, assist to close it again by drawing 

 the humerus towards the side of the body. They ;nv 



