TUB EQUrV'ALENTS OF THE SAKD. 113 



cles of tte southern hemisphere, the edge of 

 the upper mandible is fui'nished -tt-ith a thin 

 membranous skin projecting considerably on 

 each side, adding thereby to the breadth of the 

 bill. The skin covering the bill, especially 

 about the tip and along the sides, and the 

 additional membrane, in such species as pos- 

 sess it, are supplied very freely with multi- 

 tudinous nerves (from the fifth pair,) which 

 endow it with most acute discriminating sensi- 

 bility. In accordance with this sensibility of 

 the beak, the tongue, instead of being thin and 

 horny, as is the case in so many birds, is large 

 and fleshy, and furnished along its margin, and 

 on other parts, with somewhat rigid and comb- 

 like appendages. It is abundantly supplied 

 with nerves, and co-operates with the mandi- 

 bles in the discrimination and the appropriation 

 of its food. On looking at the skidl of the com- 

 mon tame swan, now before us, we find the 

 sides of the beak near the base, and the whole 

 of the tip of the upper mandible, a middle line 

 excepted, numerously perforated Avith orifices 

 for the passage of nerves; and the tip of the 

 lower mandible presents the same character. 

 Those who have seen the duck probing and test- 

 ing the mud, or watched the swan with his long 



