PHYLUM CHORDATA 



473 



wing, by which the bird rises into and propels itself through 

 the air, is performed by the pectoralis (Fig. 2S6, pet), an 

 immense muscle having about one-fifth the total weight of 

 the body ; it arises from the whole of the keel of the 

 sternum [car. si), from the posterior part of the body of 



Aw /. prptffm prn b 



cor.brhr ■gU\ t "^/Unabr tnx.acc \c^et.cp.rd I ' — 



8b.cLv 

 cor.br la cor /$¥ff^-r^r 



Fig. 286. — Columba livia. The principal muscles of the left wing; the greater 

 part of the pectoralis (pet) is removed, car. si, carina sterni: cl, furcula; cor, 

 coracoid; cor. br. br, coraco-brachialis brevis; cor. br. Ig, coraco-braclralis 

 longus; cp. st, corpus sterni; ext. cp. rd, extensor carpi radial is; c.xt. cp. ul, 

 extensor carpi ulnaris; /I. cp, ul. flexor carpi ulnaris; gl. c, glenoid cavity : hu, 

 head of humerus; hu' , its distal end ; pet, pectoralis; pet', its cut edge; /r/",its 

 insertion; prn. br, pronator brevis; prn. Ig, pronator longus; Pr. pigm, pre- 

 patagium; pt. ptgm, post-patagium ; sb. ch>, sub-clavius; sb. civ , its tendon of 

 insertion passing through the foramen triosseum, and dotted as it goes to the 

 humerus; tns. ace, tensor accessorius; tns.br, tensor brevis; tns. Ig, tensor 

 longus; tns. m. p, tensor membrane posteriori* ala^. 



that bone {cp. sf), and from the clavicle {cl), filling nearly 

 the whole of the wedge-shaped space between the body 

 and the keel of the sternum, and forming what is commonly 

 called the " breast " of the bird. Its fibres converge to 

 their insertion (J>cf) into the ventral aspect of the humerus 



