204 THE SKELETON. 



The infraspinous fossa is much larger than the preceding ; towards its verte- 

 bral margin a shallow concavity is seen at its upper part ; its centre presents a 

 prominent convexity, whilst towards the axillary border is a deep groove, 

 which runs from the upper towards the lower part. The inner two-thirds 

 of this surface afford attachment to the infraspinatus muscle ; the outer fourth 

 is only covered by it, without giving origin to its fibres. This surface is 

 separated from the axillary border by an elevated ridge, which runs from the 

 lower part of the glenoid cavity, downwards and backwards to the posterior 

 border, about an inch above the inferior angle. The ridge serves for the 

 attachment of a strong aponeurosis, which separates the Infraspinatus from the 

 two Teres muscles. The surface of bone between this line and the axillary 

 border is narrow in the upper two-thirds of its extent, and traversed near its 

 centre by a groove for the passage of the dorsalis scapula vessels ; it affords 

 attachment to the Teres Minor. Its lower third presents a broader, somewhat 

 triangular surface, which gives origin to the Teres Major, and over which 

 glides the Latissimus Dorsi ; sometimes the latter muscle takes origin by a few 

 fibres from this part. The broad and narrow 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 aponeurosis 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 from the infraspinous fossa ; it commences at the vertebral border by a 

 smooth triangular surface, over which the Trapezius glides, separated from the 

 bone 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 supraspinous fossa, and affords attachment to 

 part of the Supraspinatus muscle. Its inferior surface forms part of the infra- 

 spinous fossa, gives origin to part of the Infraspinatus muscle, and presents 

 near its centre the orifice of a nutrient 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 tl:o 

 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 con- 

 cave, 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 supraspinous 

 and infraspinous fossae. 



The acromion process, so called from forming the summit of the shoulder 

 (dxpov, a summit; V<>j, 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 con- 

 cave. 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. 



