claws, and rendered them incapable of removing 

 these parasitical nuisances from their feathers. 

 I sent the birds to the country, where they soon 

 recovered their wonted health. 



Birds are in every respect admirably adapted, 

 by their structure, to the functions they are to 

 perform ; as is beautifully seen in the organiza- 

 tion whence they acquire the power of flying. 

 To enable an animal to support itself, and to 

 make progress in the air, it is necessary, in the 

 first place, that it should be of a specific gravity, 

 not much exceeding that of the atmosphere. 

 Nature has rendered birds very light, a peculi- 

 arity which they owe partly to their very capa- 

 cious lungs, which are capable of great dilatation 

 from the remarkable mobility of the walls of the 

 chest, and partly to the extension of the lungs into 

 the abdomen, by means of membranous sacs, and 

 into the skeleton, by means of canals, so that the 

 whole body distended with air, which is rarified 

 by a considerable degree of heat (being about 

 ten degrees above that of other warm-blooded ani- 

 mals), and clothed in feathers almost as light as 

 air itself requires but a moderate degree of force 

 to support itself in the atmosphere. Expanded 

 wings, moved by very powerful muscles, enable 

 them to strike the air with a power, and to repeat 

 the stroke with a rapidity, of which no other ani- 

 mal is capable ; and thus sustaining their light bo- 

 dies, to cleave the skies with wonderful rapidity. 

 Huinboldt saw the enormous vulture of the Andes, 

 the majestic condor, dart suddenly from the hot- 



