12G - OSTEOLOGY. 



portions of bone above alluded to are separated by an oblique line, which runs 

 from the axillary border, downwards and backwards ; to it is attached the aponeu- 

 rosis separating the two Teres muscles from each other. 



The Spine is a prominent plate of bone, which crosses obliquely the inner 

 four-fifths of the dorsum of the scapula at its upper part, and separates the 

 supra-spinous from the infra-spinous fossa : it commences at the vertebral border 

 by a smooth triangular surface, over which the Trapezius glides, separated by a 

 bursa ; and, gradually becoming more elevated as it passes forwards, terminates in the 

 acromion process which overhangs the shoulder-joint. The spine is triangular and 

 flattened from above downwards, its apex corresponding to the posterior border ; its 

 base, which is directed outwards, to the neck of the scapula. It presents two 

 surfaces and three borders. Its superior surface is concave, assists in forming the 

 supra-spinous fossa, and affords attachment to part of the Supra-spinatus muscle. 

 Its inferior surface forms part of the infra-spinous fossa, gives origin to part of the 

 Infra-spinatus muscle, and presents near its centre the orifice of a nutritious canal. 

 Of the three borders, the anterior is attached to the dorsum of the bone ; the 

 posterior, or crest of the spine, is broad, and presents two lips, and an intervening 

 rough interval. To the superior lip is attached the Trapezius, to the extent shown 

 in the figure. A very rough prominence is generally seen occupying that portion 

 of the spine which receives the insertion of the middle and inferior fibres of this 

 muscle. To the inferior lip, throughout its whole length, is attached the Deltoid. 

 The interval between the lips is also partly covered by the fibres of these muscles. 

 The external border, the shortest of the three, is slightly concave, its edges thick 

 and round, continuous above with the under surface of the acromion process; 

 below, with the neck of the scapula. The narrow portion of bone external to this 

 border serves to connect the supra-spinous and infra-spinous fossas. 



The Acromion process, so called from .forming the summit of the shoulder 

 (axpov, a summit ; /*<>{, the shoulder), is a large, and somewhat triangular process, 

 flattened from behind forwards, directed at first a little outwards, and then curving 

 forwards and upwards, so as to overhang the glenoid cavity. Its upper surface 

 directed upwards, backwards and outwards, is convex, rough, and gives attachment 

 to some fibres of the Deltoid. Its under surface is smooth and concave. Its 

 outer border, which is thick and irregular, affords attachment to the Deltoid 

 muscle. Its inner margin, shorter than the outer, is concave, gives attachment 

 to a portion of the Trapezius muscle, and presents about its centre a small oval 

 surface, for articulation with the scapular end of the clavicle. Its apex, which 

 corresponds to the point of meeting of these two borders in front, is thin, and has 

 attached to it the coraco-acromial ligament. 



,Of the three borders or costae of the scapula, the superior is the shortest and 

 thinnest ; it is concave, terminating at its inner extremity at the superior angle, 

 at its outer extremity at the coracoid process. At its outer part is a deep 

 semicircular notch, the supra-scapular, formed partly by the base of the coracoid 

 process. This notch is converted into a foramen by the transverse ligament, and 

 serves for the passage of the supra-scapular nerve. The adjacent margin of 

 the superior border affords attachment to the Omo-hyoid muscle. The external 

 or axillary border is the thickest of the three. It commences above at the lower 

 margin of the glenoid cavity, and inclines obliquely downwards and backwards to 

 the inferior angle. Immediately below the glenoid cavity is a rough depression 

 about an inch in length, which affords attachment to the long head of the Triceps 

 muscle ; to this succeeds a longitudinal groove, which extends as far as its lower 

 third, and affords origin to part of the Subscapularis muscle. The inferior third 

 of this border, which is thin and sharp, serves for the attachment of a few fibres 

 of the Teres major behind, and of the Subscapularis in front. The internal or 

 vertebral border, also named the base, is the longest of the three, and extends 

 from the superior to the inferior angle of the bone. It is arched, intermediate in 

 thickness between the superior and the external borders, and that portion of it 

 above the spine is bent considerably outwards, so as to form an obtuse angle with 



