The objects which present themselves to the notice of the Natural Historian, on the surface of this globe, exhibit innumerable varieties of form, structure, action and position. But, however diversified in appearance, they readily admit of distribution into various groups, each including numerous species, capable of farther arrangement into subordinate tribes. The most extensive pf these groups, are two in number,–the one called the Organized,–the other the Inorganic Kingdom. The limits which separate these two divisions, are so well defined, that the distinction has been universally received.

Philosophers and poets, in all ages, have been anxious to point out a certain gradation of perfection in earthly objects,–a CHAIN OF BEING, the links of which consist of all created beings, passing by insensible degrees from the simplest to the most complicated, and constituting one harmonious whole, unbroken and dependent. Crystallization, they say, is the highest link of the inanimate part of the chain, and connects the Mineral with the Vegetable Kingdom. The lichen which encrusts the stone, is but one step higher in the scale of being than the stone itself. The mushrooms and corals, form a bond of union between the Vegetable and Animal Kingdoms; and the vast interval by which Man is separated from his Maker, is occupied by different orders of superior intelligences.

The ultimate object which the zoologist has in view, in the employment of the preceding methods of investigation, is to complete the History of Species. For the full accomplishment, however, of this end, it is not only necessary to acquire a knowledge of their structure and functions, but likewise of all their mutual relations. This last task can only be executed, by calling to our aid the principles of arrangement, and by distributing animals into divisions or classes, according to the characters which they exhibit. Attempts of this kind have been made by numerous observers; and the various systems which have been proposed, differing from one another in the characters employed, and the divisions recognised, intimate very plainly the difficulties inseparable from the subject.

The methodical investigation and distribution of Animals, would be comparatively easy, if the forms and modifications of the different systems of organs exhibited constant mutual relations. Thus, if we consider the organs of any system to be in their most perfect state, when they admit into their structure the greatest variety of combinations, and execute the greatest number of motions or functions, does it happen, that, when we have discovered in any species, one system of organs in its most perfect state, all the other systems may be expected to be in the same condition.

In treating of the organs of perception, we endeavoured to ascertain the functions of the six senses, and the kind of information concerning the objects around us, which they are qualified to communicate to the mind. It now remains that we attend to the sensations themselves, in reference to the processes performed upon them by the mind, with the view of becoming acquainted with the faculties of that mysterious part of our nature.

In conducting this inquiry, it is difficult to avoid the use of ambiguous phrases; for almost every term which can be applied to mind, has been loaded with a variety of significations. It will be our aim to render obvious the meaning of the terms here employed, by the descriptions which accompany them.

When we attend to the phenomena displayed by the mind, we perceive that it exhibits certain relations to the sensations of the body, changes resulting from their production, and consequent efforts of volition.

These different states or conditions of the mind have been observed to be regulated by peculiar laws, and to be subservient to particular purposes in the animal economy. They have had bestowed on them specific appellations, to express their characters ; and they have generally been denominated the Attributes, Faculties, or (in consequence of volition producing change) Powers of the Mind. Trivial objections have been urged against the use of these terms, as implying that the mind is composed of different parts; and, consequently, not entitled to its prerogative of unity.

Although the attention of many eminent chemists has been directed to the examination of the composition of animal bodies, a great deal remains undetermined, in this difficult department of experimental research. The elementary principles which occur in the Animal Kingdom, have been ascertained with considerable precision; but the binary, ternary, or other compounds which these form, have not been investigated with so much success. As these various ingredients are brought into union in the animal system, by the agency of the vital principle, their state of combination may be expected to differ widely from the ordinary results of elective attraction. When such compounds of organization are submitted to analysis, the influence of the vital principle having ceased, the product obtained, may be regarded in many cases as modifications of the elements of the substance, occasioned by the processes employed, rather than the display of the number or nature of the ingredients as they existed previous to the analytical operations. Errors, we know, are to be guarded against in the analysis of mineral waters, arising from combinations taking place during the process, which did not exist in the compound previous to analysis. How much more necessary is it, to exercise caution in drawing our conclusions regarding the composition of animal bodies?

In this section I shall enumerate the elementary bodies, which are considered as entering into the composition of the parts of animals, and then consider the combinations which these form, or the substances in which they have been detected.

The organs which we examined in the preceding chapter, are generally considered as destined for protection, and are, therefore, placed on the exterior of the body. The bones occupy a different position. They are seated in the interior ; and while they likewise assist in protecting many important organs, they, at the same time, give stability to the frame, support to the muscles, and afford levers for the execution of locomotion.

COMPOSITION OF BONES

In considering the nature ofbone, it will be of advantage to the reader, to be made acquainted with its composition, in order to understand its mode of growth. The different parts of which bones consist, may be reduced to four; the periosteum, cartilaginous basis, earthy matter, and fat.

1. Periosteum.–This bears the same relation to the bone as the skin to the body, serving as a covering for its surface, and a sheath for the different cavities which enter it. It varies in thickness, according to the nature of the bone. Its texture is obviously fibrous ; and it possesses bloodvessels. Its sensibility indicates the existence of nerves. Where this organ covers cartilaginous processes, it is called Perichondrium.

2. Cartilaginous basis.–This part of bone apparently consists of gelatine and coagulated albumen. The gelatine may be obtained by boiling the bone, previously broken into small fragments, for a considerable time in water. If the liquor be sufficiently concentrated, it will gelatinize when cold.

In preparing this work for the public, the writer was chiefly influenced by a desire to collect the truths of Zoology within a small compass, and to render them more intelligible, by a systematical arrangement. He is not aware that there exists any work in the English language, in which the subject, in its different bearings, has been illustrated in & philosophical manner, or to which a student of Zoology could be referred, as a suitable introduction to the science. There are not wanting, it is true, many disquisitions of great value, on particular departments of the physiology and classification of Animals ; for who can enumerate the names of Tyson, Lister, Willoughby, Ray, Ellis, Hunter, Pennant, Monro, and Montagu, among the dead, and Home, Kirby, and Leach, among the living zoologists of Britain, without regarding them as extensive benefactors of the science. But the writings of these naturalists, and others which have been noticed in the body of the work, are not only rare, but expensive; so that the task of investigating the facts which have been established, or the theories which have been proposed, can scarcely, in ordinary circumstances, be entered upon. The want, indeed, of such an introduction to the study of the Animal Kingdom, as should serve as an index to the doctrines on which the classification is founded, has frequently been the subject of regret, and may probably be considered as the origin of that indifference to the science which is but too apparent in this country.

Each species of Animal is destined, in the absence of disease and accidents, to enjoy existence during a particular period. In no species, however, is this term absolutely limited, as we find some individuals outliving others, by a considerable fraction of their whole life. In order to find the ordinary duration of life of any species, therefore, we must take the average of the lives of a number of individuals, and rest satisfied with the approximation to truth which can thus be obtained.

There is but little resemblance, in respect of longevity, between the different classes, or even species of animals. There is no peculiar structure, by which long-lived species may be distinguished from those which are short-lived. Many species, whose structure is complicated; live but for a few years, as the rabbit, while some of the testaceous mollusca, with more simple organization, have a more extended existence. If longevity is not influenced by structure, neither is it modified by the size of the species. While the horse, greatly larger than the dog, lives to twice its age, man enjoys an existence three times longer than the former.

The circumstances which regulate the term of existence in different species, exhibit so many peculiarities, corresponding to each, that it is difficult to offer any general observations on the subject. Health is precarious, and the origin of diseases generally involved in obscurity.

The observations which we have ventured to offer in the former volume, relate to what may be termed the Motive, the Sentient, the Nutritive, and Reproductive Functions of Animals. The various Organs of the animal frame have been described, their actions investigated, and the important purposes of life, to which they are subservient, have at the same time been pointed out. An equally extensive field of Zoological Science remains to be investigated.

Animals are related to one another, and to the objects which surround them, in such a manner, as to be dependent on a variety of circumstances for the preservation of their existence, their dispersion over the globe, and their power of accommodation to the changes of the seasons. They are likewise to be viewed as admitting of division into classes and subordinate groups, according to the external or internal characters which they exhibit. In the investigation of these characters, a variety of methods are employed, and many rules have been prescribed, to regulate the principles of zoological nomenclature.

In order to enter more fully into these important subjects, we shall distribute the present volume into Four Parts. In the first, we shall consider the Condition of Animals in reference to their Duration, Distribution, and Economical Use. In the second, we shall treat of the Methods of Investigation employed to ascertain their structure and actions.

Under this head, it is our intention to consider the circumstances under which light, electricity and caloric, are generated in the animal system. The subject is exceedingly interesting, and it has been enriched by numerous observations, the united efforts of the naturalist and chemist. Still, however, there prevails a considerable diversity of opinion, respecting the manner in which these substances are produced, or the share which the vital principle contributes towards their developement. As these bodies frequently appear to be produced contemporaneously, in the changes to which matter is subjected, they are to be viewed in this chapter in connection, in expectation that the mode of production of one, may help to illustrate the origin of antoher.

LUMINOUSNESS OF ANIMALS.

The faculty of emitting light does not appear to be possessed by any individuals of the classes Mammalia, Birds or Reptiles, Several fishes, however, exhibit this remarkable property; particularly the Dorado, Mullet, Herring and Sprat. The Spams chrysurus, an inhabitant of the seas of Brazil, is said to be luminous in such a remark able manner, that when a few individuals are swimming in company, they emit so much light, that in & dark night a person might see to read by its aid. But considerable suspicions may be entertained on this subject, whether the light is emitted by the bodies of fish, or by the number of minute parasitical animals which adhere to the surface of the skin.

The contemplation of the works of God, as exhibited in the material world, forms one of the most suitable, gratifying, and useful employments of his rational creatures. These works present themselves to our notice under different aspects, and require the employment of various methods for their examination. The results of these investigations constitute the different branches of Natural Science.

The examination of the forms, magnitudes and motions of the heavenly bodies, is the peculiar business of the Astronomer. In the prosecution of his object, he employs measurement and calculation, for the purpose of discovering the laws by which the celestial phenomena are regulated.

The beings which constitute this terraqueous globe, are subject to various changes, in consequence of their mutual actions on one another. These the Experimental Philosopher professes to investigate. When the actions here referred to are accompanied with obvious motions, but do not produce a permanent change in the constitution of those bodies subject to their influence, they constitute those phenomena which the science of Natural Philosophy professes to examine and explain. The instruments of investigation employed in this department, like those of the astronomer, are measurement and calculation, aided by experiment. When the actions which take place among bodies, produce a permanent change in their constitution, unaccompanied with motions which admit of measurement, they are considered as belonging to the Science of Chemistry. Experiment is the only instrument of investigation which can be employed with safety in this department.