INTRODUCTION. 



V 



Laving an internal skeleton; a two-fold, that is a general and a 

 pulmonic circulation, (pulmonic means belonging to the lungs;) 

 as well as a double respiration, (breathing,) the air passing between 

 their, lungs into cells distributed through various parts of the 

 body, and even into some of the bones; by being warm-blooded, 

 oviparous, (laying eggs, from the Latin ovum — an egg,) furnished 

 with four extremities, or limbs, of which the anterior (hindmost) 

 are converted into wings, and by having their skin covered with 

 feathers; a circumstance peculiarly distinctive of the class; being 

 organized for flying, they are proportionally lighter than animals 

 of equal dimensions belonging to other classes. Their specific 

 gravity (weight,) in fact, is less than that of water, so that they 

 all float on the surface of that element; and many of them are 

 adapted for swimming upon it, or for plunging or diving into it. 

 By far the greater number, however, are confined to the air, 

 most of them obtaining their food by walking on the ground or 

 on trees, while a few procure their prey on the wing, and are 

 incapable of walking without difficulty." 



This is as much as we need say at present about the general 

 structure of 



"Birds, the free tenants of land, air, and ocean, 

 Their forms all symmetry, their motions grace." 



AVES 



Is the scientific name given to this large class of animals; it is 

 the plural of avis — the Latin for a bird, or fowl. Birds have 

 been naturally divided into three great orders — aerial, of the air; 

 terrestrial, of the earth; aquatic, of the water; aer, terra, and 

 aqua, being the Latin for the three elements named. This clas- 

 sification, however, would by no means do for scientific purposes, 

 and naturalists have adopted others founded upon the peculiarities 

 of structure or habits, nature of food, or some other circumstance 

 which might serve to distinguish one species of bird from another. 

 A consequence of this diversity of arrangement is, that different 

 names are frequently applied to the same bird, which is rather 

 puzzling to a learner; but a little study of the different systems of 

 Willoughby and Bay, Linnseus, Cuvier, Brisson, Temminck, Vigors, 

 etc., will soon enable him to get over this difficulty, and to 

 recognise a feathered friend under any one of its dozen aliases. 

 The particular branch of Natural History into which such a course 

 of inquiry would lead the student, is termed 



OENITHOLOGY. 

 This, like the rest of the ologies, stands upon Greek . feet; it 



