CHAP. PAGE * The Chapters which are taken chiefly from the original work are marked THE PHILOSOPHY OF NATURAL HISTORY. INTRODUCTION. CHAPTER I. GENERAL CHARACTERISTICS OF LIVING BODIES. NATURAL HISTORY in its largest sense embraces a very wide field of investigation. It gives the history not only of animate. but of all inanimate matter, and thus extends to the mineral as well as the vegetable and animal kingdoms. It includes an account of the form, size, color, and other sensible qualities of minerals; of their position with respect to each other; their arrangement and relations as forming parts of the globe; and their relation also to the living things which now inhabit or have inhabited it. It teaches the circumstances in which vegetable and animal differ from mineral substances. It describes their structure and powers; the conditions of their existence; the laws according to which their structure and organization are made to vary, and the relation to external circumstances which renders variation of structure necessary. It arranges the individuals of these kingdoms into groups, according to certain principles of classification. It gives each individual a place in this arrangement. It enters into the history of each one; investigates its structure, its mode of life, its relation to external nature; in short, it determines and describes in detail every particular which can illustrate the character of its existence. It is manifest that no human industry can master this whole subject. It has accordingly been subdivided into many depart 1 ments, and each department affords ample material for the inves tigation of a lifetime. But the minute details which occupy the attention of the professed naturalist, are not calculated to engage the interest of the general student, or to constitute a part of the preliminary education of the young. For these they have not the taste, nor the time. Their purpose is better answered by the study of what has been denominated the PHILOSOPHY OF NATURAL IIISTORY, & more general method of presenting the same subjects. Its purpose, beside a similar consideration of the objects of inanimate nature, is to illustrate principles according to which plants and animals are constructed; the laws by which their existence is governed; the conditions under which they come into existence, continue their existence, and terminate their existence; and thus to exhibit the plan of creation and the designs of the great Author of Nature, as they are displayed in this portion of his works. The Philosophy of Natural History is indeed little less than a system of Natural Theology drawn from the history of nature, and in no way can the power and wisdom of the Creator be more clearly illustrated. The purpose of the present work is to illustrate this subject chiefly in connection with the animal kingdom, and chiefly also with those portions of this kingdom in which animal life is exhibited in its highest and most perfect state. To attempt more than this, would open a wider theme than could be clearly or profitably treated. It is not its object to teach the details of natural history except so far as they are necessary to the illustration of principles; and the phenomena exhibited by the mineral and vegetable kingdoms will only be so far adverted to as they have some relation to the conditions under which animals exist, the functions by which their existence is maintained, the relations they bear to each other, and the character they severally manifest. If a common observer were asked in what respect an animal differs from a stone, he would answer without hesitation that it differs in being alive. If the same question were put with regard to a plant, the answer would probably be the same. Supposing it to be then inquired how the plant is distinguished from the animal; the solution might seem more difficult. Very likely, however, it would be thought sufficient to say that the animal could feel and move, and that the plant could not. In point of fact these answers are sufficiently accurate, as far as they go, and yet how few of those who would make them, actually comprehend in their full extent the meaning of the very terms in which they are expressed. Our familiarity with animal and vegetable life, and our constant habit of making the distinction between the bodies possessed of them, actually prevent our perception of the wonderful and mysterious character with which they are invested. Till the conditions under which a living thing exists are deliberately considered, it is impossible fully to appreciate how strange and interesting is the simple possession of life. It impresses us most forcibly when viewed in its connection with the ordinary laws of matter, and in those species in which its attributes are most variously displayed. Strictly speaking, life is as completely possessed by the lowest plant as by the highest animal; but we can best appreciate its wonderful character when we consider it in connection with ourselves. When a man dies, his body is speedily decomposed. If the results of its decomposition are examined, it is found to have been made up chiefly of water, nitrogen, a little phosphorus, a little sulphur, some charcoal and lime, with a few other earthy and some saline ingredients. But there is nothing peculiar in the materials of which it is composed. They are elements which are constantly present in the universe about us, and which enter into the composition of a thousand other bodies. They have in themselves, separately considered, none of those properties which are found in the animal into whose composition they enter. Indeed, their original physical and chemical tendencies are actually at variance with the relation they maintain to each other as component parts of a living system; so much so, that if the mysterious bond of connection which holds them together be dissolved by death, they separate sooner or later from each other, in conformity with their original and inherent tendencies. This mysterious bond is the Principle of Life. By its influence we are enabled to maintain our existence in the midst of agents which are constantly seeking our destruction. Our bodies Fire, are composed of elements which exist everywhere in the matter around us, but gathered into new combinations and moulded into peculiar forms. The tendency of the common laws of matter is to dissolve these combinations and destroy these forms. air, and water, the cold of winter and the heat of summer, are alike our enemies. We have a chemical composition of our own, a temperature of our own, a power of spontaneous motion of our own. We maintain them in spite of the chemical affinities, the temperature, and the mechanical influences of the bodies that surround us. Deprive us of life, and our resistance to all these tendencies is at an end. Our power of motion is lost, and we yield at once to the force of gravity which brings us to the earth;- our temperature falls or rises to that of the medium by which we are surrounded ; and the chemical laws of matter, sooner or later, resolve our bodies into their original elements. We are so familiar with the spectacle of life in nature around us, as well as with the consciousness of our own existence, that we are apt to lose sight of what is most wonderful in animals and in ourselves. We wonder at the strange and curious chemistry of digestion; at the nice mechanism of the heart; at the beautiful adjustment of the eye and ear, and their adaptation to light and sound. The greater wonder is that we can exist at all in the midst of a material world constituted as it is, and governed as it is by fixed laws. Consider these laws: of Gravitation, universal, unerring, inevitable. Governing an atom as it governs a planet. Ruling all bodies, at rest or in motion, by one immutable principle. Of Heat, no less absolute and irresistible, — always tending to distribute itself in certain regulated proportions to all substances, and in the accomplishment of its laws producing the most violent effects, cleaving rocks and tearing open hills. Of Chemical Affinity, extending its sway over the same substances as the preceding, but for purposes entirely distinct. By its agency solid bodies dissolving and disappearing in apparently inert and impotent liquids; airs changing into liquids and liquids into solids; fire springing up in the midst of water, and water increasing the intensity of fire. |