ORNITHOLOGY: 



THE NATURAL HISTORY OF BIRDS. 



LESSON I. 



CLASS OF BIRDS. Zoological Characters of Birds. Peculiari- 

 ties of their Organization. 



GENERAL NOTIONS ABOUT BIRDS, 

 Of the Organization of Birds, 



1. THE CLASS OF BIRDS comprises all vertebrate animals that 

 are the best organized for flying. They are readily distinguished 

 by the general form of the body, and by the feathers with which 

 they are covered ; but the most important characters possessed 

 by them, consist in the structure of their internal organs, and the 

 manner in which their various functions are performed. 



2. In fact, they are oviparous vertebrata, in which the circula- 

 tion is double and complete ; the heart has four cavities; the blood 

 is warm, and the respiration is aerial, and double. 



3. To distinguish them from other vertebrate animals, it is 

 only necessary to say, they have a complete circulation and a 

 double aerial icspiration; or simply to remember that they are 

 the only oviparous vertebrata having warm blood. 



4. The general form of birds varies very little, and is in rela- 

 tion to the mode of locomotion which is peculiar to them. They 

 rarely attain a very large size, and their abdominal or posterior 

 extremities are especially designed for standing and walking, 



1. What animals compose the class of birds ? By what characters are 

 birds readily distinguished from other animals ? In what important particu- 

 lars do birds differ from other animals? 



2. What are birds? What is the character of the circulation in birds? 

 How many cavitie-; has the heart ? Are birds cold blooded animals ? What 

 is the character of the respiration in birds ? 



3. How are birds distinguished from other vertebrate animals ? 



4. What is remarked of the general form of birds? To what purposes 

 are the lower extremities of birds applied ? What are the functions per- 

 formed by their superior, or thoracic extremities ? What are these extremi- 

 ties called ? 



