294 I>TRODCCTION TO ZOOLOGY. 



Digestive Orr/ans. — If, quitting for a moment the consiflera- 

 tion of the feathered tribes, we cast our eyes on those of the 

 nest and hip^hest division of vertebrated animals, we find the 

 mammaha subsisting on a great variety of food — on grasses, 

 grain, fruit, seeds, and herbage — on insects, worms, and mol- 

 lusca — on the flesh of various reptiles, fishes, birds, and on 

 that of animals of their cwn class ; and, if vre 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 predicted 

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

 bird, and were required to describe the structure necessar}'^ to 

 enable a race of feathered, two-legged animals to subsist 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 worked by muscles of sufficient power — an arrangement j 

 inconsistent with the lightness which is absolutely essential. 

 This problem we have suppose d has already received its solu- ; 

 tion. The organs we would have thought most needful are f 

 altogether omitted, and their functions are performed by an f 

 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 downwai'ds ; in the Avocet (Fig. 

 246), it is long, and curved upwai'ds ; 

 in the Snipe it is a probe ; in the 

 Fig. 246.-BILL OF AVOCET. Swallow, a fly-trap; in the Duck, a 



shovel, and at the same time a strainer ; 

 by the parrot it is used as a help in climbing ; by the Vultui*e 

 (Fig. 255) as a carving knifo for his gory feast. 



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



