ORDER CETACEA. 479 



which is a kind of large pouch or air-bladder, placed in 

 the interior of the two branches of the lower jaw, and ex- 

 tending along the under part of the body. This pouch, 

 which may be considered as a kind of swimming-bladder, 

 the animal can inflate at pleasure with the atmospheric air 

 received through his spiracles, and thus increase his body 

 to a diameter of eleven feet, while, by lightening its specific 

 gravity, he is enabled to move with double swiftness. 



One of the organs of the Balaense most worthy of consi- 

 deration is the eye. In concluding this article we shall 

 examine the relations of its structure with the liquid ele- 

 ment, when we shall treat more particularly of the different 

 senses of these animals, and of those of the Common Whale 

 especially : at present we shall just glance at the situation 

 of this organ. 



In almost all the Balaense the eye is equally remote from 

 the spiracles and the extremity of the muzzle. It is situ- 

 ated on a sort of small convexity raised above the surface 

 of the lips, and which permits the animal to direct this 

 organ so as to consider an object somewhat remote, and to 

 see it with both eyes at once. The eyes are widely sepa- 

 rated, and placed immediately above the commissure of 

 the lips, and consequently very near the shoulder. The 

 crystalline is altogether conformed like that of fishes. 

 Their eye is furnished with lids like those of other Mam- 

 malia, from which, however, they differ, in being almost 

 immovable, in consequence of the quantity of oily 

 fat which inflates the interior. There are also no eye- 

 lashes. 



The eyes of the Balaense are in general very small in pro- 

 portion to the enormous volume of the head and body. In 

 the Common Whale, the largest of these animals, the dia- 

 meter of the eye is scarcely the hundredth and ninety-second 

 part of the total length of the body. 



