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NATURAL THEOLOGY. 



more artificial. Every one must have observed, 

 that the breast-bone of a fowl extends along the 

 whole body, and that the body is very large com- 

 pared with the weight : this is for the purpose of 

 rendering the creature specifically lighter and 

 more buoyant in the air ; and that it may have a 

 surface for the attachment of muscles equal to 

 the exertion of raising it on the wing. This com- 

 bination of lightness with increase of volume is 



[A, section of the fomnr, or thigh-bone, to show the hollow of 

 its shaft, and the cancellated structure of its upper and lower 

 ends ; b, the head, by which it is articulated to the pelvis ; c, the 

 ;^rcat trochanter ; d, the surface by which it is articulated to the 



