156 THE BEAK. 



orgaii in breaking hard substances, or in assisting in 

 the operation of cHmbing. 



All beaks, whether used for one purpose or for 

 another, have a cousiderable resemblance to each 

 other, not only in the shape but in the mode of using. 

 They are alv^•ays cutting or bruising instruments, the 

 effect of which is produced by pressing the one 

 against the other, and not by striking with the point 

 or darting, as is the mode of action in many bills. 

 The forms of the tomia or cutting edges, are therefore 

 the leading distinctions of different beaks, and the 

 indexes to the different characters of the owners in 

 so far as these depend upon those instruments ; 

 though there are also some corresponding differences 

 in the shape and strength. In the tomia of beaks 

 there is a slight resemblance to the teeth of animals, 

 as indicating the nature of their food. Those which 

 are carnivorous have the tomia irregular in their 

 outline, approaching in form to something like a 

 tooth ; and those which are more exclusively vege- 

 table feeders, have the lines of the tomia less broken, 

 and the acting surfaces adapted simply for breaking 

 or bruising rather than for tearing asunder. Some of 

 the latter are, however, more strongly formed than 

 any of the former ; because the shells of some fruits 

 upon which certain species at times feed, require 

 more force to break them, than is required to tear 

 the average consistency of the flesh of animals, even 

 in the most recent state. But the bills of the most 

 vegetable feeders have little or no lateral motion by 

 which they can prepare the food for the stomach by 

 grinding ; and that appears to be the chief reason 

 why birds of this description ahva^'s have muscular 

 gizzards, strong in proportion as their food is more 

 diflicult of division. 



