310 INTRODUCTION TO ZOOLOGY. 



sideration of the feathered trihes, we cast our eyes on those 

 of the next and highest division of vertehrated animals, we 

 find the mammalia subsisting on a great variety of food on 

 grasses, grain, fruit, seeds, and herbage on insects, worms, 

 and mollusca on the flesh of various reptiles, fishes, birds, 

 and on that of animals of their own class ; and, if we examine 

 the structure of their mouths, we find that they are furnished 

 with teeth so especially adapted for the several varieties of 

 food, that the habits of the animal can with certainty be pre- 

 dicted from a glance at these efficient organs. Had we never 

 seen a bird, and were required to describe the structure neces- 

 sary to enable a race of feathered, two-legged animals to sub- 

 sist on the like variety of food, we would probably consider a 

 supply of teeth, resembling those of the mammalia, but less in 

 size, as the very first requisite. These teeth would require to 

 be fixed in jaws of corresponding strength and weight, and 

 these jaws to be Avorked by muscles of sufficient power an 

 arrangement inconsistent with the lightness which is absolutely 

 essential. This problem we have supposed has already received 

 its solution. The organs we would have thought most needful 

 are altogether omitted, and their functions are performed by 

 an apparatus so unlike in structure, and yet so efficient in its 

 working, that it declares, on the part of its Artificer, an 

 amount of skill, of knowledge, and of power alike unlimited. 

 The bill, being the instrument by which food is taken, first 

 demands our examination. It is, externally, of a horny tex- 

 ture, and exhibits great variety in its form, and no less in the 

 uses to which it is subservient. In 

 some tribes, it is simply an organ for 

 prehension, used in picking up grains 

 or worms. In others, it is employed 

 to separate the seeds from the husks. 

 In the Ibis (Fig. 278), it is long and 

 bent downwards ; in the Avocet (Fig. 

 246), it is long, and curved upwards; 

 in the Snipe it is a probe; in the 

 Swallow, a fly-trap; in the Duck, a 



Fig. 246. BILL OP AVOCET. 111, , 



shovel, and at the same tune a 



strainer; by the Parrot it is used as a help in climbing; by 

 the Vulture (Fig. 255) as a carving knife for his gory feast. 

 But, supposing the food to be procured, it is needful, in 

 the next place, that there should be some convenient receptacle 



