ORDER ACCIPITRES. 99 



which are least employed. We may, thus, divine before- 

 hand the habits of an animal, by observing the organs which 

 are most developed. Thus we find the gallinaceous birds, 

 which run remarkably well, fly with extreme heaviness, and 

 the penguins, &c., which swim with such rapidity, have merely 

 pinions incapable of sustaining them in the air ; from this we 

 see, that these animals are necessitated to adopt the mode of 

 living which their organization has prescribed. 



All birds provided with long legs, like the grallae, must have 

 a long neck, and many vertebra, because they must seize their 

 prey on the ground ; but a long neck is not always accompa- 

 nied by long legs, instance the swans and other palmipedes'; 

 for these aquatic species having only to plunge their heads to 

 the bottom of marshy water, have need of nothing but short 

 oars to swim with. 



Birds with those long legs, or stilts, (from which circumstance 

 they are called ^chassiers by Cuvier,) have no need of a tail so 

 much extended as those with short feet, to serve as a helm in 

 their flight. In fact, the grallae turn their legs behind when 

 they fly, and use them like a tail. On the contrary, those 

 with short feet, as the promerops, aras, &c., have received 

 from nature a tail remarkably long. 



Notwithstanding that there are other species of animals 

 capable of supporting themselves in the air, such as the vesper- 

 tilio, the galeopithecus, the roussette, among the mammalia ; 

 the flying-dragon, among the reptiles, many species of flying- 

 fish, and an infinite number of winged insects ; and though the 

 ostrich and some other birds cannot fly, still the capacity of 

 flying is the principal faculty which distinguishes this class of 

 animals. Their body is of an oval form, evidently conformed 

 for the execution of this movement. The dorsal spine, ossified 

 and inflexible, presents a basis of support for the violent action 

 of the wing ; a sternum, widened like a sort of breastplate, 

 with a long longitudinal keel in the middle, presents powerful 

 attachments to the motive muscles of the wing, and a consider- 



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