116 



NATURAL HISTORY. 



some peculiarities in the digestive organs, most birds hav- 

 ing, in place of the process of mastication, a crop to soak 

 their food and a gizzard to grind it. 



197. Feathers have some resemblance to hairs, but di 

 fer from them in some important respects. A feather 

 has commonly three distinct parts : a horny tube, or quill 

 part; a stem proceeding from this tube; and laminae, 

 which are commonly joined together by barbs or teeth 

 on their edges. The laminae thus locked together enable 

 the feather to press upon the air in flight. In what is 

 called down the laminae are very narrow, and are entire- 

 ly separate. 



198. The wing may be considered as a hand with a 

 feathery appendage, so that it may press upon consider- 

 able air at once, and thus raise up the bird. According- 

 ly, we find that the bones of the wing are essentially the 



same as those in the arm 

 and hand of man. In Fig. 

 96 we have the bones of a 

 bird's wing. Comparing 

 this with the correspond- 

 ing part of the skeleton 

 of man in Fig. 1, we have, 

 I., the elbow-joint ; II., the 

 wrist ; III., the knuckle- 

 joint ; , the arm-bone ; 5, 

 the bones of the fore-arm ; 

 c, the bones correspond- 

 ing to those in the body 

 of the hand ; o, the thumb- 

 bone ; 1, 2, 3, 4, attempts 

 at fingers. These rudi- 

 mentary fingers, you see, 

 are very different from the 

 fingers in the wing of a 

 Bat, Fig. 20. There they 

 Fig. 9c.-Bones of Gyrfoicon's Wing, needed to be long as frame- 



