CONTENTS. CHAPTER I. Life common to Animals and Vegetables-Essence of Life-Animals distinguished from Vegetables-Of the susceptibility to Conscious- ness-Senses through which external things excite Knowledge. Of the Guiding Excitements-Of the Production of Knowledge by Ex- Language-Facts of the Origin of Particular and General Names- Progressive tendency of Language-Alphabet, Writing, Printing, Erroneous Consciousness-Deceptions of the Senses-Dreaming- ERRATA. Page 45 for "produce effect" read, produce effort. 61 for "dispsiotion" read, disposition. 80 for "fol" read, following. 129 for" as was shewn by Sir Humphry Davy," read, as was shewn by Sir Humphry Davy with respect to heat. 182 for "functions" read, function. 187 for "considering all causes. there is, &c. There is" &c., read, considering all causes, AN ESSAY, &c. CHAP. I. Life common to animals and vegetables-Essence of life-Animals distinguished from Vegetables-Of the susceptibility to consciousnessSenses, through which external things excite knowledge. LIFE is common to animals and vegetables; all the members of these two great classes of earthly productions are said to be alive during that period in which they exhibit the ability which constitutes a living existence: after the cessation of this ability, though the matter of which the animal or vegetable is made, may for a short time retain a somewhat similar form to that which it had during life, and must for ever continue in some shape or other to exist, and form part of the universe; still by general consent it is said to be dead; to have lost its vitality; to be lifeless; the assertion merely signifying, that it has ceased to be possessed of the characteristics which it was wont to have, and commenced the exhibition of others. Life is a vortex or whirlpool of material motions. The animal to support its life, at intervals takes into its stomach a quantity of matter: this undergoes a process of change from the action of juices such as the gastric juice, the bile and the pancreatic juice, and after having been dissolved to a jelly, that portion that is suitable to the support of the body is separated from that which is not so; the latter is ejected from the system, the former is absorbed by suitable organs from the surface of the intestines, and is thus taken into the structure, into the various constituents of which, whether solids or fluids, it becomes changed for a time, but is eventually reduced to a state that may be called vapourous or gaseous, and thrown off from the skin, in perspiration and exhalation. In the vegetable, the nutriment instead of being taken into the system from the inner coat of the stomach, is absorbed by roots fixed in materials capable of supplying this nutriment. The particles enter at the root, for a time form part of the structure of the plant, and are ultimately thrown off from its various surfaces, in vapours, gasses, perfume, or effluvia. There is then in the living substance a continued process of material change taking place, which includes the two great functions of nutrition and waste. It is this whirlpool of matter that constitutes life: the ability to sustain it is the ability to live, and is considered to be the essence of life. As long as this ability continues, the animal or vegetable is living; when it ceases, the animal or vegetable is dead.* It may be laid down as a general rule, to which however there seem some slight exceptions, that vegetables do not indicate the susceptibility to feel, nor the power to move about. They derive their nutriment from the moisture amidst which they spring, and there is no necessity for their moving about to seek food. With the animal however there is such a necessity, for the matter qualified to support it is scattered, and its existence would be impossible without the power to move in quest of food. To do this, there must in the first place be machinery to perform the requisite motions; then there must be a guiding principle to superintend the motions; and also there must be an impelling principle to move the animal. The machinery in some animals, such as worms, consists merely of muscles, in the larger both bones and muscles are used. The skeleton acts as a framework for the support of the softer bodily constituents, and some of its parts are levers, which are moved by the muscles to produce certain motions of the animal. The muscles are those portions of the flesh that we commonly call the lean. They may in some instances be likened to a number of ropes binding the different * Vide Cuvier's Animal Kingdom. |