STRUCTURE OP FOOT. ORGANS OP SENSE. 375 



of which these Birds seize their prey, either to tear it to pieces 

 on the spot, or to carry it away with them. In Birds adapted 

 to live on the shores of rivers, and to seek by wading the worms 

 and fish which constitute their food; the feet are slender, of 

 extreme length, and bare below the knee (Fig. 286), an 

 arrangement very favourable to this kind of life, and which has 



FIG. 190. FOOT OF GANNET. 



procured for these birds in France the name of Echassiers (stilt 

 birds), from Echasse (stilt). Again in the kinds formed for 

 living on deep water, the feet are palmated, or webbed ; that is, 

 transformed into a swimming apparatus, by the addition of a 

 membrane which extends between the claws without preventing 

 them from separating ; a character which is observable in Ducks, 

 Swans, and a number of aquatic Birds. 



339. The sense of touch is but little developed in Birds ; 

 the feathers which clothe the whole body oppose great obstacles 

 to the exercise of this faculty, and the peculiar conformation of 

 the organs of prehension is equally unfavourable to it. Taste 

 is more or less obtuse in these animals ; their tongue is generally 

 cartilaginous, and destitute of nervous papillse ; and they appear 

 almost always to swallow their food without masticating it. 

 The organ of smell is more perfect, without presenting, however, 

 all the high development which is found in the Mammalia. 

 The nasal fossae are sunk in the base of the upper mandible, 

 and do not communicate with sinuses ; their surface is covered 

 with a very vascular pituitary membrane, and is extended by 

 three cartilaginous plates (analogous to the spongy lones of 

 Mammalia, ANIM. PHYSIOL., 506), turned on themselves and 



