84 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



Fig. 108. — The dorsal surface of the left scapula (£). 



Fig. 109. — The costal surface of the left scapula (J). 



Fig. 1 10. — The left scapula seen from the outer angle and axillary border (£). 



Fig. hi. — The left clavicle seen from below (§). 



Fig. 112. — The left clavicle seen from above (§). 



This border receives the insertion of the serratus magnus muscle, which also extends outward upon the costal 

 surface in the vicinity of the superior and inferior angles, so that the costal surface presents two shallow triangular areas 

 for the attachment of muscles, in addition to the subscapular fossa. 



The superior border presents a notch, the scapular notch (Figs. 108 and 109), which may 

 be either deep or shallow, and to the outer side of this there projects from the superior margin 

 a strong, curved, hook-like process, the coracoid process (Fig. 109). This arises by a broad 

 base between the scapular notch and the outer angle, and is at first directed upw r ard and some- 

 what forward; it then becomes narrower, makes a distinct turn, and passes forward and out- 

 ward to end in a roughened apex. 



The axillary border (Fig. no), so called because it is directed toward the axilla, is slightly 

 thickened and roughened, particularly toward the external angle. A furrow separates this 

 elevated border from the anterior surface of the bone. 



The internal angle is either a right or an obtuse angle; the inferior one is acute with a mark- 

 edly rounded apex. At the external angle is situated the so-called head of the scapula, which 

 presents the articular surface for the head of the humerus, the glenoid cavity (Fig. no), which 

 is smooth, slightly concave, and shaped like a pear with the apex upward. 



Above the glenoid cavity is a small surface, the supraglenoidal tuberosity (Fig. no), which 

 gives origin to the narrow cord-like tendon of the long head of the biceps, and below the cavity 

 there is a larger, markedly roughened surface, the injraglenoidal tuberosity, which gives origin 

 to the broad strong tendon of the triceps. The head of the scapula is separated from the 

 remainder of the bone by a slight constriction called the neck. 



The spine of the scapula (Fig. 108) arises by a broad base from the dorsal surface between 

 the supraspinatous and infraspinatous fossae, and gradually becomes higher as it passes from 

 the vertebral border to the neck of the bone. It passes over the neck, overhangs the glenoid 

 cavity from above and behind, and terminates in a strong, broad, flattened process, the acromion. 

 Internal to its apex, the acromion presents an elongated, flat, articular surface for the attach- 

 ment of the acromial end of the clavicle. 



The scapula is preformed in cartilage during fetal life. The first center of ossification appears in the third month 

 of embryonic life in the region of the neck, but ossification proceeds so slowly that large areas are still cartilaginous in 

 the new-born. During the first year of life an independent center appears in the coracoid process,* from which is formed 

 the greater portion of this projection. At the age of puberty special epiphyseal centers make their appearance, in the 

 apex and the base of the coracoid process, in the acromion (usually several centers), in the base of the scapula, in the 

 inferior angle, in the glenoid fossa (usually somewhat later), sometimes in the margin of the spine of the scapula, and 

 (even earlier, in the tenth year) in the external angle of the scapula in the region of the origin of the biceps tendon. 



* In reptiles, birds, and the lowest mammalia the coracoid process is an independent bone. 



