LIFE.

THERE are some tendencies in the philosophy of the day which appear to us dangerous. They are the more so, perhaps, because we have the evidences of experiment brought forward to support the favourite view. Were it not that the tendencies, to which we allude, are found to a greater or a less extent in every work on natural philosophy, and physiology, and in many works on chemistry, we should not deem it necessary to speak of them.

We refer to the view entertained that Life—the vital energy is merely the result of the combined operation of the physical forces; or, as is supposed by many, merely a modified form of electrical energy.

It appears to us, that a clear conception of the visible phenomena of Life may be arrived at by a little careful study of certain fixed conditions:- that such a study will tend to prove, that the vital force is not only, none of the physical forces under any modification, but that it is something which controls the action of them all; and, beyond this, it will teach us that that which sees will never be seen; that the power which feels will never be perceptible by human sense. We would consider Life in its lowest and in its highest form,-the little plant, which with its foliage and its flowers lends a beauty to external Nature, and Man, created to be the monarch of the world. Attempts have been made but not hitherto in any instance with complete -to draw the line between the vegetable and the animal kingdom. Linnæus propounded the law,—that plants grow and live, that animals live and move; but we know of plants which move, and of animals having no powers of locomotion. Chemists have drawn the distinction

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A PLANT COMING TO LIFE.

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by saying that plants yield oxygen to the air, and animals carbonic acid; but some of the lowest orders of animals yield oxygen, as the plant does, and a large variety of plants part with carbonic acid in the same way as was once thought to be peculiar to the animal alone. The vegetable and the animal races shade so gradually one into the other, that we cannot mark the ending of the first or the beginning of the last.

A vital power-Life-differing only in degree, is found pervading the entire system of organisation.

Let us commence our inquiry at the beginning :-the seed, with its latent life, buried in the soil. If we make a vertical section of a seed, we discover the embryo surrounded with starch and gluten. The seed is placed in the soil; darkness, a certain temperature and moisture are required for healthful germination. Let us mark what takes place; the seed swells, it developes heat, it becomes sweet to the taste, and it gives out carbonic acid.

A pile of barley, moistened, in a dimly-lighted place, will, as it germinates, develope heat, which a thermometer will show daily increasing. We know that the barley, in becoming malt, acquires sweetness; the fact being, that in germination the starch is converted into sugar, by the absorption of oxygen from the air. The seed, therefore, is in the condition of a burning body, consuming oxygen gas and producing carbonic acid,—a compound of carbon with oxygen.

Under these influences Life begins, and the embryo grows; but neither the chemical action nor the heat are the Life. The cotyledons ascend, the roots descend, and the plumula, or first leaf-bud, is forced above the soil; and the young creation, escaping from darkness, rejoicing in light, undergoes an entire change in its economy.

The plant now takes from the air, by its leaves, carbonic

acid; and under the influence of light it decomposes this carbonic acid, retains the carbon to form its wood, and sets the oxygen free into the air. It has frequently been stated that this decomposition of carbonic acid in the plant is due to light. It is only so indirectly. The plant, by virtue of its vital power, decomposes this compound air; but light quickens, by its mysterious powers, the living energies; and, as the light increases, the power of decomposing carbonic acid increases in a direct ration, and it diminishes regularly with the diminution of luminous force; but during the entire life of the plant it never either by day or by night, ceases to effect this decomposition. During darkness, the life of the plant is in a condition of repose; this chemical action is at its minimum; with the first touch of the sunbeam it awakens into energy, as every fibre pulsates anew under the quickening power of the morning rays. We have the power of collecting the gases given off by the leaves from a plant, and thus of measuring the amount of action going on at any given hour. It has been found that if, when under the influence of bright sunshine each leaf upon a branch is sending forth its oxygen, a wound, merely a puncture with a fine needle, be made at the base of the branch, every leaf is sensible of the injury, and its vital labours are checked.

Surely we perceive something here beyond either Solar Light, Heat, or Chemical Action-an independent Vitality. In the seed, all the phenomena of heat and chemical action may be established without producing Life (growth). Certain delicate conditions are required. In the dead plant we may have also an enormous amount of chemical action— Heat, and even Light developed, but yet no LIFE.

Man must be regarded as the highest type of the animal economy, and in every way he represents the conditions of animal existence in its most exalted form.

Lavoisier said, "The fable of Prometheus is but the outshadowing of a philosophic truth; where there is Light, there we find organisation and Life; where Light cannot penetrate, Death for ever holds his silent court."

LIGHT is especially necessary to the animal; the deprivation of it is fatal to his healthful existence. HEAT is necessary; and under all conditions of climate, a mean animal temperature is preserved by the processes of respiration and digestion. The carbon element of our food passes into the blood; it meets with oxygen in the lungs, and being virtually burnt, is passed off into the air as carbonic acid. By the process of combining carbon and oxygen, Heat is developed, as it is in the burning of a coal or a candle.

Quarles, in his "Emblems," without being conscious of it, advances from imaginative Poetry to the purest and the truest Philosophy, when he pursues his emblem of the Taper, the type of Life.

Again, ELECTRICITY is manifested in every movement of the body, and almost in every effort of the mind. Hence it is, that some philosophers have supposed the brain to be a system of voltaic cells, and the nerves a series of conductors; the senses, indeed, being but the out-stations of an electrical telegraph, which convey along the wires intelligence to the great central station, the brain.

No one will deny the importance of all these forces,Light, Heat, Chemical power, and Electricity, are necessary for the maintenance of Vital energy in the animal frame. They are a mysterious bond of forces-each having its especial function.

But in decomposing dead animal matter, we have all these acting with greater power than in the living system. The controlling power of LIFE is strikingly shown in cases of sudden, especially sudden violent death. A healthy man is thrown from his horse and killed on the spot-the gastric

juice in a few hours dissolves not merely the contents of the stomach, but the stomach itself. Life, the controlling power, is gone, and chemical action pursues unchecked its ravages.

Electricity is such a wonder-working agent, that it has become a sort of fashion to refer every phenomenon which we do not understand in some way or other to the influence of electricity. It cannot, however, be too distinctly stated that there is not, within the entire range of electrical enquiry, one experiment which proves that any of the functions. of Life can be maintained by electricity. Experiments in support of the electrical theory of vitality have been published; but under the careful examination of properly guarded minds, the fallacy of these has in every case been shown.

The physical forces we can examine-we can torture them to tell us the secrets of many of their laws—we can chain them to our tasks, and compel them to do our bidding. We may advance to a more refined knowledge of these great natural energies than that which we at present possess, and we probably shall discover forces which are superior in action to those which we already know. But vital force cannot be detected by the natural philosopher-it cannot be traced by the anatomist or the physiologist-it cannot be analysed by the chemist. The greatest mechanician of us all cannot control it. We rashly attempt to grasp it—it eludes us, and a dead mass is all that is left us to study.

There are bounds beyond which the searching powers of the human mind cannot venture, and if human fancy on wild wing essays the proscribed region, it flutters in convulsions, and falls back to earth exhausted by its fruitless efforts.

The connexion, however, of all those great Energies, with both vegetable and animal life, must never be lost sight of, and we are enabled to trace all the physical forces to their source-the centre of the solar system-the Sun.