540 MAMMALIAN ANATOMY 



the scapula, and also in the position of its highest point. Its edge may 

 be almost straight or strongly sinuate, and either sharp for the greater 

 part of its extent or in part or wholly flattened and retroverted. 



The metacromion is quadrate, triangular, or rounded, and rarely 

 not denned above from the edge of the spine. The degree of its intro- 

 version also varies. 



The acromion presents at least two variations in direction. In one 

 form its long axis is a continuation of the long axis of the spine, 

 and its tip projects below the glenoid cavity when the bone is seen 

 directly from the side ; in the other form the axis is bent forward 

 from the axis of the spine, and the tip is opposite the neck of the 

 bone. The tip is pointed, or blunt, swollen, and slightly bifid ; traces 

 of the epiphyseal suture are sometimes visible. 



The triangular flattened region at the top of the axillary border 

 for the teres major is rarely wanting. 



The suprascapular notch varies in depth and in the degree of 

 prominence of the angle which its upper limit forms with the anterior 

 superior border. 



The subscapular fossa varies, of course, in form, and also in the 

 degree of development of its tendinous ridges. Rarely the ridges are 

 practically absent, The third ridge is frequently wanting. The 

 bevelled area along the axillary border may be broad and obscurely 

 defined from the rest of the surface. The depression at its lower end 

 may be deepened into an excavation. 



The coracoid process is measurably constant, varying slightly in 

 its direction and in the acuteness or bluntness of its tip. 



The supraglenoid tubercle appears to be always present, although 

 at times it is small and rounded. The general outline of the glenoid 

 cavity is constant, but it may vary in size and in relative breadth 

 from without inward. The area of origin of the scapular head of the 

 triceps on the axillary border sometimes encroaches on the lower 

 margin of the cavity and makes it straight ; occasionally the tendon 

 of the supraspinatus grooves the upper outer margin. 



HUMAN SCAPULA. 



The scapula of man (Figs. 424, 425) presents all the parts shown in 

 the scapula of the cat except the metacromion. It has in addition an 

 articular facet on the inner border of the acromion, for union with the 



