BIRDS. 565 



being anchylosed together for this purpose ; so 

 that they form a bone of great length. The 

 coccygeal vertebrae (Q) are also numerous, but 

 are compressed into a small space, and enjoy 

 great latitude of motion, being subservient to the 

 movements of the tail. 



The ribs are numerous, and of considerable 

 strength : they send out processes, which are 

 directed backwards, passing over the next rib 

 before they terminate, and giving very effectual 

 support to the walls of the chest. The ribs are 

 continued along the abdomen, and afford pro- 

 tection to the viscera in that cavity ; and some 

 arise even from the sacrum, and from the iliac 

 bones. Those which are in front are united to 

 the sternum (s) by means of sternal appendices, 

 which are ossified, and appear as the continu- 

 ations of the ribs, or as if the ribs were jointed 

 in the middle. 



The sternum is of enormous size, extending 

 over a considerable part of the abdomen, and 

 having a large perpendicular crest descending, 

 like the keel of a ship, from its lower surface. 

 The object of this great developement is to 

 furnish extensive attachment to the large pectoral 

 muscles employed to move the wings, and which, 

 taken together, are generally heavier than the 

 rest of the body. Considered with reference to 

 all the other muscles, and to the weight of the 

 body itself, these pectoral muscles are of enor- 

 mous strength. The flap of a swan's wing is 



