Useful Knowledge: Volume 3. Animals / Or, a familiar account of the various productions of nature

INTRODUCTION.

1. Animals are natural bodies which possess organization, life, sensation, and voluntary motion; and ZOOLOGY is that branch of natural science which treats of their systematic arrangement; their structure and functions; their habits of life, instincts, and uses to mankind.

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.

		With vertebrÆ	brace	Hot blood	brace	Viviparous	I.	Mammalia.
Body	brace					Oviparous	II.	Birds.
				Cold red blood	brace	With lungs	III.	Amphibia.
						With gills	IV.	Fishes.
		Without vertebrÆ. Cold white blood			brace	Have antennÆ.	V.	Insects.
						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.

5. The second class, or BIRDS, comprises all such animals as have their bodies clad with feathers. Their jaws are elongated, and covered externally with a horny substance called a bill or beak, which is divided into two parts called mandibles. Their eyes are furnished with a thin, whitish, and somewhat transparent membrane, that can at pleasure be drawn over the whole external surface like a curtain. Birds respire by air-vessels, which are extended through their body, and which, in the abdominal cavity, adhere to the under surface of the bones. Their organs of motion are two wings and two legs; and they are destitute of external ears, lips, and many other parts which are important to quadrupeds.

6. LinnÆus has divided this class into six ORDERS.

ORDERS OF BIRDS.
1. Land Birds.
I.	Rapacious Birds (Accipitres)	Have the upper mandible hooked, and an angular projection on each side near the point, as the eagles, hawks, and owls.
II.	Pies (PicÆ)	Have their bills sharp at the edge, somewhat compressed at the sides, and convex on the top, as the crows.
III.	Passerine Birds (Passeres)	Have the bill conical and pointed, and the nostrils oval, open, and naked, as the sparrow and linnet.
IV.	Gallinaceous Birds (GallinÆ)	Have the upper mandible arched, and covering the lower one at the edge, and the nostrils arched over with a cartilaginous membrane, as the common poultry.
2. Water Birds.
V.	Waders (GrallÆ)	Have a roundish bill, a fleshy tongue, and the legs naked above the knees, as the herons, plovers, and snipes.
VI.	Swimmers (Anseres)	Have their bills broad at the top, and covered with a soft skin; and the feet webbed, as the ducks and geese.

7. Under the third class, or AMPHIBIA, are arranged such animals as have a cold, and, generally, naked body, a lurid colour, and nauseous smell. They respire chiefly by lungs, but they have the power of suspending respiration for a long time. They are extremely tenacious of life, and can repair certain parts of their bodies which have been lost. They are also able to endure hunger, sometimes even for months, without injury.

The bodies of some of them, as the turtles and tortoises, are protected by a hard and horny shield or covering; those of others are clad with scales, as the serpents, and some of the lizards; whilst others, as the frogs, toads, and most of the water-lizards, are entirely naked, or have their skin covered with warts. Many of the species shed their skins at certain times of the year. Several of them are furnished with a poison, which they eject into wounds that are made by their teeth.

They chiefly live in retired, watery, and morassy places, and, for the most part, feed on other animals; though some of them eat water plants, and many feed on garbage and filth. None of these species chew their food; they swallow it whole, and digest it very slowly.

The offspring of all the tribes are produced from eggs, which, after they have been deposited by the parent animals in a proper place, are hatched by the heat of the sun. The eggs of some of the species are covered with a shell: those of others have a soft and tough skin or covering, not much unlike wet parchment: and the eggs of several are perfectly gelatinous. In those few that produce their offspring alive, as the vipers, and some other serpents, the eggs are regularly formed, but are hatched within the bodies of the females.

8. This class is divided into two ORDERS.

ORDERS OF AMPHIBIA.
I.	Reptiles	Have four legs, and walk with a crawling pace, as the tortoises, frogs, and lizards.
II.	Serpents	Have no legs, but crawl on their belly.

9. Fishes constitute the fifth class of animals. They are all inhabitants of the water, in which they move by certain organs called fins. These, when situated on the back, are called dorsal fins; when on the sides, behind the gills, they have the name of pectoral fins; when on the belly near the head, they are ventral; when behind the vent, they are anal; and that at the posterior extremity of the body is called the caudal fin. Fishes breathe by gills, which, in most of the species, are situated at the sides of the head. In some of the flatfish, however, as the skate and thornback, they are on the under part of the body. Fish rise and sink in the water, generally by a kind of bladder in the interior of their body, called an air-bladder. Some of them, as the skate and other flat-fish, do not possess this organ, and consequently are seldom found but at the bottom of the water. The bodies of these animals are usually covered with scales, which keep them from injury by the pressure of the water. Several of them are enveloped with a fat and oily substance to preserve their bodies from putrefaction, and also to guard them from extreme cold.

10. The fishes are divided into six ORDERS.

ORDERS OF FISHES.
I.	Apodal	Have bony gills; and no ventral fins, as the eel.
II.	Jugular	Have bony gills; and the ventral fins situated in front of the pectoral fins, as the cod, haddock, and whiting.
III.	Thoraic	Have bony gills; and the ventral fins situated directly under the pectoral fins, as the perch and mackerel.
IV.	Abdominal	Have bony gills; and the ventral fins on the belly behind the pectoral fins, as the salmon, herrings, and carp.
V.	Branchiostegous	Have their gills destitute of bony rays.
VI.	Chondropterygeous	Have cartilaginous fins, as the sturgeons, sharks, and skate.

11. The fifth class of animals comprises the INSECTS. These are so denominated from the greater number of them having a separation in the middle of their bodies, by which they are, as it were, cut into two parts. The science which treats of them is called ENTOMOLOGY.

Insects have, in general, six or more legs, which are, for the most part, nearly of equal length and thickness. Sometimes, however (as in the mole-cricket), the forelegs are very thick and strong, for burrowing into the ground; sometimes the hind thighs are long and thick, for leaping; or flattened, fringed with hairs, and situated nearly in an horizontal position, to serve as oars for swimming.

Most of the insect tribes are furnished with wings. Some, as the beetles, have two membranous wings, covered and protected by hard and crustaceous cases, called elytra; some, as the wasps and bees, have four wings without elytra; others, as the common houseflies, have two wings; and others, as the spiders, are entirely destitute of these members.

They are furnished with antennÆ, which are usually jointed, and moveable organs, formed of a horny substance, and situated on the front and upper part of the head. These serve as instruments of touch, or of some sense which is to us unknown. The eyes of insects are formed of a transparent substance, so hard as to require no coverings to protect them. Their mouth is generally situated somewhat beneath the front part of the head, and in a few of the tribes is below the breast; and the jaws are transverse, and move in lateral directions. These are furnished with feelers, and other organs, of various arrangement and structure, which constitute the foundation of arrangement in some of the systems of entomology. All insects breathe, not through their mouth, but through pores or holes along the sides of their bodies; or, as in the crabs and lobsters, by means of gills. The skin of insects is, in general, of hard or bony consistence, divided into plates or joints which admit of some degree of motion, and is generally clad with very short hairs.

Nearly all insects go through certain great changes at different periods of their existence. From the egg is hatched the larva, grub, or caterpillar, which is destitute of wings; this afterwards changes to a pupa, or crysalis, wholly covered with a hard shell, or strong skin, from which the perfect or winged insect, bursts forth. Spiders, and some other wingless insects, issue from the egg nearly in a perfect state.

12. LinnÆus has divided the animals of this class into seven ORDERS.

ORDERS OF INSECTS.
I.	Coleopterous	Have elytra or crustaceous cases covering the wings; and which, when closed, form a longitudinal division along the middle of the back, as the chafer.
II.	Hemipterous	Have four wings, the upper ones partly crustaceous, and partly membranous; not divided straight down the middle of the back, but crossed, or incumbent on each other, as the cock-roach.
III.	Lepidopterous	Have four wings covered with fine scales, almost like powder, as the butterflies and moths.
IV.	Neuropterous	Have four membranous and semi-transparent wings, veined like net-work; and the tail without a sting, as the dragon-fly and ephemera.
V.	Hymenopterous	Have four membranous and semi-transparent wings, veined like network; and the tail armed with a sting, as the wasp and bee.
VI.	Dipterous	Have only two wings, as the common house-flies.
VII.	Apterous	Have no wings, as the spiders.

13. The sixth and last class of animals consists of WORMS, or vermes. These are slow of motion, and have soft and fleshy bodies. Some of them have hard internal parts, and others have crustaceous coverings. In some of the species eyes and ears are very perceptible, whilst others appear to enjoy only the senses of taste and touch. Many have no distinct head, and most of them are destitute of feet. They are, in general, so tenacious of life, that parts which have been destroyed will be re-produced: These animals are principally distinguished from those of the other classes by having tentacula, or feelers.

14. Some late writers have divided the worms into three or more distinct classes; but the LinnÆan division is into five ORDERS.

ORDERS OF VERMES, OR WORMS.
I.	Intestinal	Are simple and naked, without limbs; some of them live within other animals, as the ascarides and tape-worms; others in water, as the leeches; and a few in the earth, as the earth-worm.
II.	Molluscous	Are simple animals, without shell, and furnished with limbs, as the cuttle-fish, medusÆ, star-fish, and sea-urchins.
III.	Testaceous	Are animals similar to the last, but covered with shells, as oysters, cockles, snails, and limpets.
IV.	Zoophytes	Are composite animals, and appear to hold a rank between animals and vegetables; though they are in fact true animals, and possess sensation and voluntary motion. In many instances a great number of them inhabit the same stone, but some are soft, naked, and separate. The coral, sponge, and polypes, are instances of this order.
V.	Animalcules	Are destitute of tentacula or feelers, and are generally so minute as to be invisible to the naked eye. They are chiefly found in different infusions of animal and vegetable substances.

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