196 FACULTIES OF BIRDS. 



upper surface is smooth, and where it joing the head 

 there is a circular flap which lies loose upon the hair ; 

 the under surface of this portion is also smooth, but 

 has two hard ridges of a horny nature, situated longi- 

 tudinally on each side of the middle line of the bill. 

 The lower mandible of the bill is much smaller than 

 the upper, and when opposed to it, the upper lip 

 extends beyond it for the whole of its breadth *." 



The structure which has just been described is 

 exactly similar to that of geese and ducks, whose bills 

 are covered with an extremely sensible skin, supplied 

 with an abundance of nerves from all the three branches 

 of the fifth pair, an apparatus that enables them to 

 feel about for their food in mud, where Blumenbach 

 (mistakirigly as it seems to us) supposes they can 

 neither see nor smell it f. 



Skull of the Duck, showing; the distribution of the fifth pair of nerves to 

 the upper mandible, and the serratures on the edge of the lower ja\v. 



M. Majendie is disposed to restrict the term tact, 

 amongst other things, to the perceptions of heat and 

 cold ; but though we do not consider the restriction 

 happy, there can be no doubt of the sensation being 

 considerably different from others peculiarly ascribed 

 to touch, though we may not, with Darwin and 

 Fleming, refer them to a distinct sense. Dr. Fleming 

 distinguishes what he terms the sense of heat from 



* Home's Lectures, i. 304. f Comp. Anat. 224. 



