LIGAMENTS OF SCAPULA. 37 



the hinder half, and above to the line on the tinder-surface of the 

 clavicle, which extends outwards from the tubercle before mentioned. 

 The two pieces of the ligament are in apposition behind, but are 

 usually separated by an interval in front. 



Both pieces of the ligament support the scapula in a state Use of liga-' 

 of rest. They serve also to restrain the rotatory movements of that ment * 

 bone ; thus, when the acromion is rotated down, the motion is 

 checked by the trapezoid Ijand, and when upwards by the conoid 

 piece. 



ACROMIO-CLAVICULAR ARTICULATION. The articular surfaces of Joint with 

 the clavicle and acromion process of the scapula are connected acronl 

 together by a capsule, which is thick above (superior ligament), but capsule, 

 very thin below. 



An intemrticular fibro-cartilage is sometimes present at the upper fibro-carti- 

 part of the joint ; and occasionally it forms a complete septum. If age ' 

 the fibro-cartilage is perfect, there are two synovial cavities in the and synovial 

 joint ; if it is imperfect, there is only one. The joint should be ** 

 opened to see the cartilage and the synovial sac. 



Movements. This articulation allows the scapula to change its Use of 

 position in relation to the clavicle when the former bone is moved, Jom " 

 either in gliding over the surface of the thorax, or in being rotated 

 with the elevation and depression of the arm. 



SCAPULAR LIGAMENTS. The special ligaments of the scapula are Ligaments 

 twu in number, and extend from one point of the bone to another. 



1. The SUPRASCAPULAR LIGAMENT ( 4 ) is a narrow band stretching supra- 

 aeross the notch in the upper border of the bone. By one end it is 

 attached to the base of the coracoid process, and by the other to the 

 border behind the notch. It converts the notch into a foramen, 

 through which the suprascapular nerve passes. 



2. The CORACO-ACROMIAL LIGAMENT ( 3 ) is triangular in form, and coraco- 

 extends transversely between the acromion and the coracoid process. 

 Externally it is inserted by its apex into the tip of the ucromion ; 



and internally, where it is much wider, it is attached to all the 

 outer border of the coracoid process, reaching backwards to the 

 capsule of the shoulder-joint. The ligament consists usually of two formed of 

 thickened bands, anterior and posterior, with a thinner intervening 

 part. It forms part of an arch above the shoulder-joint, which pre- use. 

 vents the head of the humerus being displaced upwards. 



Dissection. The supraspinatus muscle should now be laid bare, Dissection, 

 the acromion process sawn through, and turned aside with the outer 

 end of the clavicle. A strong fascia will be seen to cover the sur- 

 face of the supraspinatus muscle, and is to be taken away after it 

 has been observed. 



The SUPRASPINATUS MUSCLE (fig. 13, A) has the same form aa the Supraspina- 

 hollow of the bone which it fills. It arises from the surface of the 

 supraspinous fossa of the scapula, except over the neck, from the "g in " 

 upper side of the spine of the bone, and from the fascia covering its 

 surface. Its fibres end in a tendon, which crosses over the 

 shoulder-joint, and is inserted into the upper impression on the insertion ; 

 great tuberosity of the humerus. 



