32 MORPHOLOGY OF THE VERTEBRATA. 



which point it forms externally the posterior portion of the- 

 glenoid cavity. Internally it is produced to meet the clavicle, 

 while at the remainder of its anterior surface it affords strong 

 attachment to the coracoid. The scapula is placed longitudinally, 

 extending backwards from the shoulder, parallel to the vertebral 

 column, to which, however, it presents a slight eonvexity. Its 

 posterior third is bent downwards at a slight angle. It extends, 

 over four ribs. 



CORACOID 



Is the strongest of the bones entering into the formation of the 

 scapular arch. Its inferior end is expanded transversely, and is 

 received into the corner groove at the anterior margin of the body 

 of the sternum, before described. Its direction is upward, out- 

 ward, and forward, to the shoulder joint, where it is firmly 

 articulated with the scapula and clavicle, forming with the former 

 the "glenoid cavity for the head of the humerus; at the inner 

 side of the humeral end it affords an articular surface for th& 

 clavicle. 



THE CLAVICLES 



Are very early anchylosed into a V-shaped single bone, known 

 as the furculum (merrythought). 



The apex of the V is united with the keel of the sternum by a 

 band of fibrous tissue. The principal use of this furcular arch is- 

 to act in opposition to the forces which tend, during the down- 

 ward stroke of the wing, to press the coracoid inwards, and also 

 by an elastic reaction to restore them to their proper position. 



FORE-LIMB OR WING 



Consists of a humerus, radius and ulna, two carpel bones, meta- 

 carpel and phlanges. 



THE HUMERUS 



Lies parallel to the axis of the body when the fore-limb is in a 

 state of rest, while the fore-arm is in a condition midway between 

 pronation and sipination. The proximal end of the humerus 

 is transversely expanded, and at its extreme end presents a 

 convex articular surface, which fits into the glenoid cavity of the 

 shoulder joint ; on either side of this end is a ridge, which gives 

 insertion to the pectoral muscles. Its distal end exhibits two- 

 facets, the outer being for articulation with the ulna, and the 

 inner with the radius. 



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