44 ANATOMY. 



Describe the Clavicle. The collar- or key-bone, is a short bone by struct- 

 ure, having no medullary canal ; and is curved like the letter f, its inner 

 two-thirds being cylindrical, and convex anteriorly ; its outer third flattened, 

 and concave anteriorly. It is placed horizontally between the sternum and 

 the scapula, and is the most elastic bone in the body. It presents, from within 

 outwards, the following points, viz. 



Facets, for articulation with the sternum and the cartilage of the 1st rib, at 

 its sternal end. 



Impression for the rhomboid, or costo-clavicular ligament. 



Groove, on the lower surface, for the subclavius muscle. 



Tubercle, for the conoid part of the costo-clavicular ligament. 



Oblique Line, for the trapezoid part of the same ligament. 



Facet, on the acromial end, for articulation with the scapula. 



Nutrient Foramen, in the subclavian groove. 



Describe the Scapula. The shoulder-blade is a large, flat, and triangular 

 bone, situated on the posterior and lateral portion of the thorax, from the 2d 

 rib to the 7th, inclusive. 



THE VENTER, or anterior surface, presents from within outwards, 

 Ridges, giving attachment to the subscapularis muscle. 

 Marginal Surface, along the inner border, for the attachment of the serratus 



magnus muscle. 



Subscapular Fossa, and Angle, for the subscapularis muscle. 

 THE DoRSUM, or posterior surface, presents the following, viz. 



Spine, a bony ridge, which affords attachment to the trapezius and deltoid 



muscles, and ends in the acromion process. 



Supraspinous Fossa, above the spine, for the supraspinatus muscle. 

 Infraspinous Fossa, below the spine, larger than the supraspinous, convex at 



its centre, lodges the infraspinatus muscle, and the nutrient foramen. 

 Marginal Surface, along the external border, to which are attached the teres 

 minor muscle above, the teres major below, and sometimes a few fibres of 

 the latissimus dorsi at the lower angle. 

 Groove crossing the margin, for the dorsalis scapulae vessels. 

 Smooth Surface, behind the root of the spine, over which the trapezius 



muscle glides. 



THE ACROMION PROCESS, or "summit of the shoulder," extends from the spine, 

 and projects over the glenoid cavity, articulating with the clavicle by an oval 

 facet. It affords attachment to the deltoid and trapezius muscles, and by its 

 apex to the coraco -acromial ligament. 



THE CORACOID PROCESS, or " crow's beak," projects from the upper border 

 and neck of the bone over the inner and upper part of the glenoid cavity. 



