STERNUM OF THE JACKO PARROT. 357 



tion between structure and use in those parts of birds, 

 even those parts which are not immediately con- 

 nected with each other, to find that the same quan- 

 tity and power of motion (however different the 

 object) are accompanied by the same general form of 

 the posterior portion of the sternum ; and there is 

 still this other relation between the action of the 

 feet in these otherwise dissimilar tribes of birds, that, 

 though they are both powerful clutchers, the one in 

 killing game, and the other in climbing among twigs, 

 they are both very imperfect walkers on the ground. 



When we come to examine the anterior part of 

 the sternum that on which the character of the flight 

 more immediately depends, we find that, though the 

 wing of the parrot must, from both the depth of the 

 keel and the breadth of the sternum, be a ready wing, 

 yet it must be comparatively feeble and unsteady. 



The lower ends of the coracoids do not form an an- 

 gle of about sixty degrees, with these edges attached 

 to the sternum, as is the case in all the falconidae 

 of powerful wing ; neither are their axes directed 

 toward the strongest part of the keel of the sternum, 

 either when viewed in front or on the side, as those 

 of the falcons are when viewed both ways. Their 

 union with the sternum, though not quite a straight 

 line, is upon the whole at right angles to the axis of 

 the body when seen in front, and they are nearly 

 parallel to each other ; and though enlarged at the 

 heads, not nearly so robust as those of the falcons, 

 although rather longer in proportion. In their 

 articulation on the sternum, and their position with 

 regard to each other, they have thus very little stiff- 

 ness in resisting the approach of the shoulder joints 

 toward each other ; thus in this respect they are to a 

 great extent the very opposite of those of the falcons. 



