THE SCAPULA. 179 



divided into two cavities by the spine, which is stretched from 

 behind forwards, much nearer to the superior than to the inferior 

 costa. The cavity above the spine is really concave, where 

 the supra-spinatus muscle is lodged ; while the surface of this 

 bone below the spine, on which the infra-spinatus muscle is 

 placed, is convex, except a fossa that runs at the side of 

 the inferior costa. 



The internal or anterior surface of this bone is hollow, except 

 in the part above the spine, which is convex. The subscapu- 

 lars muscle is extended over this surface, where it forms 

 several ridges and intermediate depressions, commonly mis- 

 taken for prints of the ribs : they point out the interstices of 

 the bundles of fibres of which the subscapularis muscle is 

 composed. 



The spine rises small at the base of the scapula, and becomes 

 higher and broader as it advances forwards. On the sides it is 

 unequally hollowed and crooked, by the action of the adjacent 

 muscles. Its ridge is divided into two rough, flat surfaces : into 

 the upper one the trapezius muscle is inserted ; and the lower 

 one has part of the deltoid fixed to it. The end of the spine, 

 called acromion, or top of the shoulder, is broad and flat, and is, 

 sometimes, only joined to the spine by a cartilage. The anterior 

 edge of the acromion is flat, smooth, and covered with a cartilage, 

 for its articulation with the external end of the clavicle ; and it is 

 hollowed below, to allow a passage to the infra and supra-spinati 

 muscles, and free motion to the os humeri. 



The coracoid process is crooked, with its point inclining for- 

 wards ; so that a hollow is left at the lower side of its root for 

 the passage of the subscapcularis muscle. The end of this pro- 

 cess is marked with three plane surfaces. Into the internal, 

 the pectoralis is inserted ; from the external, one head of the 

 biceps flexor cubiti rises ; and from the lower one, the coraco- 

 brachialis has its origin. At the upper part of the root of this 

 process, immediately before the semilunar cavity, a smooth 

 tubercle appears, where a ligament from the clavicle is fixed. 

 From the whole of the external side of this coracoid apophysis 



