The Electro-Magnetic Telegraph has made the action of its battery familiar to most of our readers. A number of plates of zinc and copper are arranged alternately in a vessel containing an acid. When the extremities of the apparatus are joined by means of a wire, however long, a chemical action begins upon the surface of the zinc, and a force is propagated along the wire, by which we can raise weights, set wheels in motion, and decompose compounds, the elements of which have the strongest affinity for each other. The moment the continuity of the wire is interrupted and the circuit broken, the force disappears, and the action between the acid and the zinc immediately stops. When the communication is restored the action of the acid upon the zinc is renewed, and the force which had vanished reappears with all its original energy. The substance of the wire, however, is merely the conductor of force, and does not contribute the slightest share to its manifestations. Something analogous to this is the office of man in regard to matter and the forces of Nature. He serves merely to give them circulation, without adding to or detracting from their quantity. His person is but a scene in the theatre of their action, in which they have their exits and their entrances, and each one in his time plays many parts, sustaining transmutations of force, and causing them; but they are immortal in their essence, and run in an endless vicissitude through a round of various utilities, for the maintenance of life and the means of life.

Our concern is with such matter and forces as are employed in human nutrition.

Man feeds upon both vegetables and animals. The animals he consumes are themselves nourished by vegetable aliment. The vegetables, in their turn, digest the inorganic elements supplied by the soil and the air. Modern chemistry has proved that the ultimate constituents of all, are Carbon, Oxygen, Nitrogen, and Hydrogen, the four principal elements of the organic creation, and sulphur, phosphorus, chlorine, lime, potassium, sodium, iron, and a few other inorganic substances.* These must be introduced into the

* “Of the human frame, bones included, only about three-fourths is solid matter-chiefly carbon and nitrogen-the rest is water. If a man weighing

vegetable or animal body, in order that it may live and grow. From these few elements, combined in different numbers and proportions, are formed air and water, the rocks and the earths, which are the result of their decomposition.

That the elements incorporated into the frame of vegetables and animals, are derived from air, water, earth, and rock, has been demonstrated by repeated experiments, exhibiting the fact that the precise quantities of the identical elements gained by the former had disappeared from the latter, under circumstances artificially arranged so as to exclude the possibility of their being drawn from other contributories than those whose loss was to be examined. For detailed accounts of the experiments and reasoning by which these conclusions are demonstrated, we refer the student to the works of Liebig, and other writers on Organic Chemistry, who have pursued the path of inquiry which he opened and so successfully wrought.

The fundamental property of vitality, common to all organized bodies, consists in their constant material renovation; an attribute which distinguishes them from the inert or unorganized bodies, whose composition is always fixed. The latter may be artificially constructed by putting together their constituent parts; while no chemical skill is adequate to the production of wood, sugar, starch, fat, gelatine, flesh, &c., whose elements, though equally simple and equally well known, refuse to combine in organized compounds, otherwise than under the operations of that mysterious power which we call vital force. The growth of a crystal-the highest inorganic process we are acquainted with, involving but one action, that of accretion-may be conducted artificially by the chemist; while the growth of a simple cell, such as compose the yeast fungus, and the

160 pounds were squeezed flat under a hydraulic press, 120 pounds of water would run out, and only 40 of dry residuum remain. A man is, therefore, chemically speaking, a little less than fifty pounds of carbon and nitrogen, diffused through six pailsful of water. Berzelius, indeed, in recording the fact, justly remarks that the living organism is to be regarded as a mass diffused in water;' and Dalton, by a series of experiments tried on his own person, ascertained, that of the food with which we daily repair this water-built fabric, five-sixths is also water.”—London Quarterly Review.

minute alge which colour the waters of stagnant pools, though the lowest organic process, involves the double action of accretion and disintegration, and defies the power of science to produce. The meanest and least complex form of life it is beyond man's reach to fashion.*

While the ultimate elements of vitality are profusely furnished in the natural world, vegetables alone have sufficient assimilative power to compose their tissues directly from inorganic matter, the liquid and gassy materials, and the earthy particles, which are but minerals decomposed. Not only so, but no part of an organized being can serve as food to vegetables, until, by the process of putrefaction and decay, it has assumed the form of inorganic matter. It is this capacity which renders vegetable organization the essential base of all other. In the absence of vegetation all animals must be carnivorous, and subsist by mutual destruction, which would soon exterminate their species. For this reason it must necessarily precede animal life. That such has been the fact is abundantly proved by geological research, which, reading the history of buried ages in the rocks, shows us that a period of long duration intervened, after the growth of lichens and ferns in the primitive world, before the lowest order of animals made its appearance upon the earth.

Animal organism, on the contrary, requires for its support and

* I am aware that the English philosopher, Mr. Crosse, supposes himself to have produced insect life, by galvanism, from a soluble glass made of pure black flints and caustic soda, dissolved in distilled water. There is no doubt of the good faith and intelligence of Mr. Crosse. Though not disposed to alter the text, I deem it proper to add this note.

†There is a race of Indians, in Utah and Oregon, who are earth-eaters. They are described in Stansbury's account of the Expedition to the Great Salt Lake, as the very lowest order of human beings. Humboldt mentions that the Otomaas, living on the banks of the Orinoco, who subsist mainly on fish, and are averse to any kind of tillage, are addicted to eating a soft, unctuous clay, which they knead into balls and roast by a weak fire. The balls are moistened again, to prepare them for being eaten. A writer in the Journal of the Royal Agricultural Society of England, (quoted in the Patent Office Report for 1851, page 503,) suggests that dirt is eaten for the purpose of supplying a deficiency of lime in the ordinary food of the tribes, in whom this practice has been observed.

development highly organized atoms. The food of animals, in all circumstances, consists of parts of organisms. While some of them feed directly upon vegetation, others, requiring that matter should have taken on a higher order of life before it can support their own, prey upon other and inferior animals. Having a lower assimilative capacity, it is necessary that their food should have been brought by intermediate agents, into combinations agreeing more nearly with those of their own tissues than even vegetable organization. Without some arrangement and gradation of this character, the higher natures must either perish for lack of food, or consume all their activity in chemical transformations, without reserving any for locomotion or other muscular effort. We may remark here, that with this necessity of overcoming and capturing prey, arises a degree of mental power, enabling the carnivorous animals to devise plans, and to compass by association with their fellows, ends beyond their unassisted power. The spider spins an artful web to catch flies, and wolves hunt their game in packs. The superior functions are everywhere united with less energy in the inferior. Those beings in whom the latter prevail are self-sufficing and independent, but have little reach and power beyond the satisfaction of the low primary wants. As we rise in the scale up to man, the crown and roof of things, we find him, of all, the most dependent, the most prone to association, for which, by the faculty of speech, he is most adapted; and by means of association, though alone the least self-sufficing of all beings, he wins the dominion over Nature and her forces, whether animate or inanimate.

Another distinction between animal and vegetable life is this. The growth and development of vegetables depends upon the elimination of oxygen from the other component parts of their nourishment. They are perpetually exhaling this gas from the surfaces of their leaves into the air. The life of animals exhibits itself in the continual absorption of the oxygen of the air, and its combination with certain component parts of the body. Its office is to generate animal heat by burning the combustible substances of the frame. It combines with the carbon of the food, and in so doing precisely the same quantity of heat is disengaged as if it had been directly burned in the air. The result is carbonic acid gas,

which is thrown out of the lungs and the skin; this is absorbed by the leaves of plants, the carbon separated and incorporated into their substance, and the oxygen again exhaled into the atmosphere, to resume its round of circulation.

Man eats the When it enters

To trace the cycle a little farther-the carbon uniting with water in the plant, forms, among other things, starch, which the sap conveys to the part requiring it. It is found largely in the seeds. Starch exists in wheat to the extent of one half the weight of the grain, and it consists of carbon and water only. wheat, but we find no starch in the human body. our frames it undergoes a chemical change, a slow burning, in fact, in which the carbon of the starch combines with oxygen, forming carbonic acid gas, which, together with the liberated water in the shape of vapour, is thrown out of the human system into the atmosphere, to be again converted in the laboratory of the plant into the starch from which they were derived. Having served our purpose in keeping up the internal warmth upon which animal life depends, the disengaged elements are recomposed by the plants into part of their substance, which when completed again serve as fuel in the animal economy.

The instances we have given, will, so far as relates to their organic constituents, suffice to exemplify the law that animals and vegetables are mutually convertible one into the other, and depend on each other for existence. The interchange of their elements is accomplished through the medium of the atmosphere from which plants derive far the greatest portion of their nutriment.* It is

* "Two hundred pounds of earth were dried in an oven, and afterwards put into a large earthen vessel; the earth was then moistened with rainwater, and a willow tree weighing five pounds was planted therein. During the space of five years, the earth was carefully watered with rain-water. The willow grew and flourished; and, to prevent the earth being mixed with fresh earth, blown upon it by the winds, it was covered with a metal plate full of very minute holes, which would exclude everything but air from getting access to the earth below it. After growing in the earth for five years, the tree was removed, and on being weighed, was found to have gained one hundred and sixty-four pounds. And this estimate did not include the weight of the leaves or dead branches which in five years fell from the tree.