STRUCTUUK OV lUllDS. d 



possible strengtli and security; and accordingly, the wliolo of tliis portion of tlic spiiio, 

 tog-etlier with tlie sacnnit — llio lionc which forms the basis of the vertebral coluiiui — is 

 consolidated into one piece. All the processes are lai-gelj- developcil, and pass obliquely 

 from one vertebra to the next, mutually locking them together; and in order most 

 effect ually to preclude the possibility of any flexion, the spinous processes, and sometimes 

 even the bodies of tlie dorsal vertebrie, are immovably soldered together by osseous matter 

 so as to form one continuous bono. 



The sacrum consists of the imion of a great niunber of vertebra?, as many as twenty 

 being miited for the same purpose, so that they form a bone of great length. The 

 coccijgeal verfehne — those connected with the lower part of the sacrum — are also numerous, 

 but are compressed into a small space, and enjoy great latitude of motion, being sub- 

 servient to the movements of the tail. 



The ribs are numerous, and of considerable strength ; they send out processes, 



FIG. 1. — SKELETOX OF A BIRn. 



FIG. 2.— STERXU.M OF BIRDS. 



which are directed backwards, passing over the next rib before they temilnate, and 

 giving very effectual sujiport to the walls of the chest. The ribs are continued along the 

 abdomen, and afford protection to the viscera in that cavity ; and some arise even from 

 the breast-bone, or sternum, and the iliac bones. Those which are in front are united to 

 the sternmn by osseous appendices, and appear as the continuation of the ribs, or as if 

 the ribs were joined in the middle. 



The sternum is of enormous size, extending oyer a considerable part of the abdomen, 

 and ha\Tug a large perpendicular crest descending, like the keel of a slup, from its lower 

 sm-face. This is designed to pro\'Ide extensive attachment to the large pectoral muscles 

 employed to move the mngs, and which, taken together, are generally heavier than the 

 rest of the body, and they are also of enormous strength. The flap of a swan's wing is 

 said to be capable of breaking a man's leg, and a similar blow from an eagle has been 

 known to prove instantly fatal. 



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