POWER OF FLYING. 483 



possible wings could be so artificially adapted to 

 the body as to receive the full force of the actions 

 of the limbs, however these actions might be com- 

 bined, they would fall very far short of the exer- 

 tion necessary for raising the body from the ground. 



Examples, however, occur in every one of the 

 classes of vertebrated animals, where an approach 

 is made to this faculty. In the Exocetus, or tlying- 

 fish, the pectoral fins have been enormously ex- 

 panded, evidently for the purpose of enabling the 

 animal to leap out of the water, and support itself 

 for a short interval in the air ; but its utmost efforts 

 are inadequate to sustain it beyond a few moments 

 in that element, and it scarcely ever rises more than 

 five or six feet above the surface of the water. 



A species of lizard, called the Draco Volans, has 

 a singularly constructed apparatus, which appears 

 like two wings, afl[ixed to the sides of the back, and 

 quite independent of either the fore or the hind ex- 

 tremities. By the aid of these moveable flaps, the 

 animal is able to descend from the tops of trees, or 

 flutter lightly from branch to branch ; but this is 

 the utmost that it can accomplish by means of these 

 imperfect organs. The construction of these anoma- 

 lous members is highly curious in a physiological 

 point of view; as showing how Nature, in effecting 

 a new purpose, is inclined to resort to the modifica- 

 tion of structures already established as constituent 

 parts of the frame, in preference to creating new 

 organs, or such as have no prototype in the model 

 of its formation. Frequent illustrations of this law, 

 indeed, are afforded by the comparative examina- 

 tion of the anatomy of the organs of progressive 

 motion. The ribs, in particular, are often the 



