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CHAP. X.

NATURAL HISTORY,

Continued.

Natural History-Zoology-General arrangement-Linnæan systemDivisions of-Linnæan classes-Mammalia-Aves-Amphibia-Pisces Insects-Vermes.

ZOOLOGY comprizes the whole animal world, or all those beings which are called by the name of Quadrupeds, Birds, Amphibia, Fishes, Insects, Testaceous animals, and Zoophytes. These latter, as we have shewn, chap viii, are of very different forms, and are allied by many resemblances to the vegetable world.

In taking a brief survey of the animal world, we shall begin with the highest order of animals, and descend to the lowest. It is not, in the present state of our knowledge, practicable to make out a continuous chain, or series of animals, united throughout by evidently connected links. It has indeed been observed, that all the productions of Nature, seem rather connected by many points of affinity, on different sides, than by a regular chain of gradation; so that the face of nature may rather said to represent a reticulated or polygonal surface, than to be disposed in a continued linear progression. If, however, a perfectly natural chain or arrangement of animals cannot be contrived, it is still necessary to form some kind of

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classification, in order to keep together such tribes as most evidently resemble each other. Hence Naturalists have invented several systems or distributions of animals, formed either from the general external appearance, or from the structure of their principal organs.

The most ancient division of animals is that of Aristotle, who divided them into viviparous, that is, those that produce living, and perfectly formed young, and into oviparous, or such as are produced from eggs. This kind of division continued to be in use with some modification, till towards the decline of the seventeenth century; when our countryman Mr. Ray, formed a new classification, founded chiefly on the structure and nature of the heart and lungs in the different tribes; and the Linnæan arrangement of the animal kingdom is, in fact, founded upon that of Ray, particularly with respect to quadrupeds.

The Linnæau system, which we shall briefly explain, with respect to the animal world, is thus distributed: 1. Into animals that have warm and red blood, and a heart divided into two cavities, or ventricles, as anatomists term them. These animals consist of quadrupeds and birds-the former being viviparous, the latter oviparous.

2. The next division consists of such animals as have a heart with a single ventricle, while the blood, though red, is of a far lower temperature than in quadrupeds and birds, so that it is commonly called cold blood. These animals consist of what are denominated by Linnæus, Amphibia, such are Tortoises, Frogs, Lizards, and Serpents; and also Fishes. The Amphibia, or the Frog, Tortoise, Lizard, and Serpent tribes, have, what Linnæus calls arbitrary lungs, or such as can suspend respiration at pleasure, for a considerable time, without injury to the animal. Fishes, instead of lungs, are furnished with gills, in which innumerable divisions of bloodvessels are disposed in semi-circular ranges.

8. The third division of animals consists of such as are supposed to have a heart with a single cavity, and a cold

whitish, or nearly colourless blood. These animals consist of Insects, and of a very numerous and diversified tribe, called by the name of worms. The former of these, viz. the Insects, are distinguished by the particular organs called antennæ, resembling small horns; while the latter, or worms, are characterized by having tentacula, or flexible feelers.

To proceed to the Linnæan arrangement. By this all animals are divided into six classes, of which, the characters are taken from the internal structure of the beings treated of. The six classes are as follow, viz. MAMMALIA, AVES, AMPHIBIA, PISCES, INSECTE, VERMES.

1. The class MAMMALIA, comprehends all such animals as suckle their young, being furnished with proper organs for the purpose. In all the animals of this class, the plan or fabric of the skeleton, as well as their internal organs, bears a degree of general resemblance to that of Man. Their outward covering consists, in general, of hair; but in some few the animal matter of the hair takes the form of distinct spines or quills, as in the Porcupine and Hedge-hog tribe. In others, the same substance is expanded into the appearance of strong and broad scales, as in the genus Manis; and in others, as in the Armadillo, instead of hair, we meet with strong bony zones or bands, forming a regular suit of armour.

The instruments of loco-motion, or feet, in the Mammalia, are generally four in number, and furnished with separate toes, guarded by claws. In some, as in the monkey tribe, the feet have the appearance of hands: in some tribes the feet are shod with strong hoofs, either entire, or divided.

In such of the Mammalia as possess the power of flight, as in the Bat tribe, the fore-feet are drawn out into slender fingers of an immoderate length, and united by a common membrane or web. In some of the aquatic mammalia, as the Seals, both the fore and hind feet are very strongly or widely webbed; and in the Whale, there are in reality, only two feet, the bones of which are inclosed in what are commonly called the fins, while the lobes of the tail answer the purpose of a

pair of hind feet. The arms, or offensive and defensive weapons of the mammalia, besides the claws and teeth, are principally the horns; inserted in various directions, and on different parts, in different tribes. The horns are either perennial or annual. In the Rhinoceros, the horn is perennial, and situated on the top of the nose. In the Deer tribe, the horns are annual, branched, covered while young with a soft villous skin or coat; they grow from the tip, and become very solid and strong at their full size. In the Ox tribe, as well as in the Sheep and Goat, they are hollow, mounted on a bony core, and grow from the base.

The teeth in quadrupeds or mammalia, are of three kinds: 1. The front or cutting teeth are of a broad, compressed structure, designed for cutting food: 2. Sharp, lengthened, or canine teeth, situated on each side the cutting teeth, and calculated for tearing and dividing the food; and 3. Grinders, with broad, angular tops, for grinding the food. The teeth, as will be seen, afford a principal character in forming the orders and genera. In some the canine teeth are wanting; in others the front teeth; and some few are totally destitute of teeth.

The tail in quadrupeds is formed by a continuation of the vertebræ, or joints of the back-bone; and is in some of great length, and covered with very long hair; in others it is very short; and in some few entirely wanting, as in the Apes.

The senses of the mammalia consist, as in man, of the organs of sight, hearing, tasting, and smelling, and the power of feeling; and in many of these animals these organs are of greater acuteness than in man. The eyes, in some quadrupeds, as the horse, are furnished with what is called a nictating membrane, or semi-transparent guard, situated beneath the eye-lids, and which can at pleasure be drawn over the ball of the eye for its defence. The nose, or organ of smelling, is more or less compressed and lengthened. In the Elephant it is extended in a most wonderful manner into a long and tubular proboscis, or trunk, at the tip of which are placed the nostrils. The teats or mammæ are found in these animals, and, as

has been observed, give rise to the Linnæan title to the whole class.

The first class of animals, or MAMMALIA, is divided into seven Orders. 1. The first of these orders is denominated Primates, as containing the chiefs of the creation. Its characters are four front or cutting teeth, above and below, and one canine or sharpened tooth on each side of these. In a mere zoological view, the human kind stands at the head of this order, forming the Linnæan genus Homo. Next to this is the genus Simia, including Apes, Baboons, and Monkeys; the Oran Outang being the chief of the tribe. The other genera of the order Primates are the Lemur, or Macauco, and the Bat.

2. The second order, denominated Bruta, is characterized by a want of front or cutting teeth, in the upper and lower jaw. The feet are armed with strong claws: their pace is in general slow, and their food is principally vegetable. Of this order the chief genera are the Rhinoceros, the Elephant, the Bradypus or Sloth, the Myrmecophaga or Ant-eater, the Dasypus or Armadillo, and the Platypus or Ornithorynchus, or Duckbill. The last, though placed among the mammalia, is a most extraordinary and dubious quadruped: it is not certain that it is possessed of any mammæ: it is a native of Australasia or New Holland, where it is found in fresh-water lakes, and is supposed to feed on worms, water insects, and various weeds, in the manner of a duck. It is obliged to rise occasionally to the surface of the water, in order to breathe.

3. The third order, called Fera, contains, among other genera; the Phoca or Seal, the Canis or Dog, the Felis or Cat, Ursus the Bear, and Erinaceus the Hedge-hog. This order contains the predacious quadrupeds, all agreeing in having teeth evidently calculated for feeding on flesh. The front teeth, which are usually six above and below, approach to a conical or pointed figure; the canine teeth are long, and the grinders not flattened at top. The claws of the feet are sharp, and more or less curved in the different species.

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