CHAPTER II.

THE ANATOMY OF A BIRD.

The Three Divisions of the Class Aves--ANATOMY OF A BIRD--The Skeleton--Distinctive Features--Peculiar Bone Character--The Skull--Difference between the Skull of Birds and that of Mammals--The Jawbones--Vertebral Column--Sternum--Fore-limbs--Hind-limbs--Toes--The Muscular System--How a Bird remains Fixed when Asleep--The Oil-gland--The Nervous System--The Brain--The Eye--The Ear--The Digestive System--The Dental papillæ--The Beak--Tongue--Gullet--Crop--Stomach--Uses of the Gizzard--Intestine--The Liver, Pancreas, and Spleen--The Blood and Circulatory System--Temperature of Blood of a Bird--Blood Corpuscles--The Heart--The Respiratory System--Lungs--Air-sacs--The Organs of Voice--The Egg--Classification of the Class Aves 239