2. The objects comprehended within the animal kingdom are divided into six classes: of Mammalia or Mammiferous Animals, Birds, Amphibia or Amphibious Animals, Fishes, Insects, and Worms: which are thus distinguished: CLASSES. { Viviparous I. MAMMALIA. { Hot blood { Oviparous II. BIRDS. { With vertebræ { Cold red blood { With lungs III. AMPHIBIA. Body { { With gills IV. FISHES. { { Have antennæ. V. INSECTS. { Without vertebræ. Cold white blood { Have tentacula. VI. WORMS. 3. The first class, or MAMMALIA, consists of such animals as produce living offspring, and nourish their young ones with milk supplied from their own bodies; and it comprises both the quadrupeds and whales. 4. This class has been distributed into seven ORDERS; of _primates_, _bruta_, _feræ_, _glires_, _pecora_, _belluæ_, and _cete_, or whales. The characteristics of these are founded, for the most part, on the number and arrangement of the teeth; and on the form and construction of the feet, or of those parts in the seals, manati, and whales, which supply the place of feet. _ORDERS OF MAMMALIA._ I. PRIMATES Have the upper _front teeth_ generally four in number, wedge-shaped, and parallel; and two _teats_ situated on the breast, as the _apes_ and _monkeys_. II. BRUTA Have no _front teeth_ in either jaw; and the _feet_ armed with strong hoof-like nails, as the _elephant_. III. FERÆ Have in general six _front teeth_ in each jaw; a single _canine tooth_ on each side in both jaws; and the grinders with conic projections, as the _dogs_ and _cats_. IV. GLIRES Have in each jaw two long projecting _front teeth_, which stand close together; and no _canine teeth_ in either jaw, as the _rats_ and _mice_. V. PECORA Have no _front teeth_ in the upper jaw; six or eight in the lower jaw, situated at a considerable distance from the grinders; and the _feet_ with hoofs, as the _cattle_ and _sheep_. VI. BELLUÆ Have blunt wedge-shaped _front teeth_ in both jaws; and the feet with hoofs, as the _horses_. VII. CETE Have _spiracles_, or breaking holes on the head; _fins_ instead of fore-feet; and a _tail_ flattened horizontally, instead of hind feet. This order consists of the _narwals_, _whales_, _cachalots_, and _dolphins_.