90 CLASS AVES. 



SUPPLEMENT ON THE GALLING. 



The birds of this order inhabit almost all the warm 

 countries of the old and new worlds. With the exception of 

 the first family (The Alectors), there are few of them which 

 have the habit of perching. Although not exactly confined to 

 any exclusive aliment, they most generally subsist on grains 

 of various kinds : and in drinking, they elevate their heads in 

 the air, for the purpose of swallowing the liquid. The 

 pigeons, however, differ in this respect, for they plunge their 

 bills into the water, and drink at a single draught. They 

 are pulverating birds, that is, they are fond of rolling in, and 

 covering themselves with dust — the principal motive for which 

 appears to be the necessity of freeing themselves from the 

 vermin which torment them. In the sexes there is a very 

 considerable difference in the plumage, until the advance of 

 age, when the female sometimes assumes the colours of the 

 male, which are the most brilliant. The female, in the great 

 majority of the species, is generally the smallest, and least 

 powerful. In comparing the gallinae to mammiferous animals, 

 with reference to internal structure, we find them exhibit 

 most analogy with the ruminantia. Like them, they have 

 three successive stomachs. The food is collected in the first 

 stomach or crop, which has but little labour to perform, the 

 grain only commencing to be softened there. Digestion is 

 begun in the second, which is glandulous, and finished in the 

 third, which is extremely powerful, and is commonly called 

 the gizzard. Redi, Magnoletti, and Reaumur, have made ex- 

 periments on the digestive powers of these birds, which have 

 been repeated and verified by Spallanzani. The researches 





