1 82 A MANUAL OF ANATOMY 



origin to the deltoid, and an intervening rough surface which is 

 encroached upon by the tendinous fibres of these two muscles. 

 The upper lip is often very projecting at its inner end, where the 

 tendon receiving the lower fibres of the trapezius is inserted. 



The acromion process is situated at the outer extremity of 

 the spine, and its direction is outwards, upwards, and forwards, 

 so as to overhang the glenoid cavity. It is somewhat triangular, 

 and is compressed from above and behind downwards and 

 forwards. The postero-superior surface, which is rough, gives 

 origin at its lower and inner part to some fibres of the deltoid, and 

 elsewhere is subcutaneous. The antero -inferior surface, which is 

 smooth and concave, overhangs the glenoid cavity, and is related 

 to the subacromial bursa. The outer border is continuous with the 

 lower lip of the posterior border of the spine, where there is a pro- 

 jection called the acromial angle, and this outer border gives origin 

 to a portion of the deltoid. The inner border is continuous with the 

 upper lip of the posterior border of the spine, near which it gives 

 insertion to a part of the trapezius, whilst near the tip of the acro- 

 mion it presents an oval facet for the outer extremity of the clavicle. 

 The upper and lower margins of this facet are rough for the acromio- 

 clavicular ligaments. The tip or apex of the process is situated 

 at the meeting of the outer and inner borders. The acromion pro- 

 cess is pierced by many arterial twigs derived from the acromial rete. 



The coracoid process, which is strong and curved, springs 

 from the upper aspect of the head, immediately external to 

 the suprascapular notch. It is directed at first upwards and 

 forwards for about ^ inch, and then, bending sharply, it 

 is directed forwards and outwards to terminate in a blunt tip. 

 The ascending portion is compressed from before backwards. Its 

 anterior surface is related to the subscapularis, and the posterior 

 to the supraspinatus. Its outer border gives attachment to a 

 portion of the coraco - humeral ligament, and the inner border, 

 which bounds the suprascapular notch externally, gives attachment 

 at its upper part to the suprascapular or transverse ligament. 

 The horizontal portion of the process is compressed from above 

 downwards. Its antero -internal border, which is long and convex, 

 and the adjacent portion of the superior surface, give insertion 

 anteriorly to the pectoralis minor, whilst posteriorly they give 

 attachment to the costo-coracoid membrane and ligament. The 

 postero-external border, which is short, receives the fibres of the 

 coraco-acromial ligament, and gives attachment to a portion of the 

 coraco-humeral ligament. At the back part of the antero-internal 

 border there is the conoid impression for the conoid ligament. On 

 the back part of the superior surface there is the trapezoid ridge 

 for the trapezoid ligament, which ridge extends forwards and out- 

 wards from the conoid impression. The inferior surface of the 

 horizontal portion is smooth and concave. The tip or apex, which 

 is blunt, gives origin to the conjoined short head of the biceps and 

 coraco-brachialis. 



