b BIRDS. 



especially the tarsal portion, which is never ap- 

 plied to the ground in the action of walking. 



Though many birds feed on hard substances, 

 their jaws are entirely destitute of teeth ; but are 

 more or less extended into two mandibles, and 

 incased in horny coverings of considerable den- 

 sity, which are exceedingly diversified in form and 

 use. " Thus in birds of prey [the beak] well exe- 

 cutes the office of a dissecting knife ; in seed- 

 eating birds it forms a pair of seed-crackers for 

 extricating the kernel from the husk which en- 

 velopes it; in the Swallows and Goat-suckers it 

 is a fly-trap ; in the Swans, Geese, and Ducks, it 

 is a flattened strainer, well furnished with nerves 

 in the inside for the detection of the food re- 

 maining after the water is strained, by that par- 

 ticular operation which every one must have ob- 

 served a common duck perform with its bill in 

 muddy water. In the Storks and Herons we 

 find it a fish-spear ; and in the Snipes and their 

 allies it becomes a sensitive probe, admirably 

 adapted for penetrating boggy ground, and giving 

 notice of the presence of the latent worm or ani- 

 malcule." * The stomach in Birds consists of three 

 parts (which are > not, however, in all cases dis- 

 tinctly developed) ; the crop or craw, the mem- 

 branous stomach or proventriculus, and the giz- 

 zard. The last, which is seen to advantage in 

 the grain-eating birds, is composed of two very 



* Penny Cyclop.; Art. BIRDS. 



