Chapter II.
Organic Nature of Man.

Characteristics of Organization.—Besides those general properties of matter to which we have already referred, we find in plants and animals a property, or power, of a very different and peculiar kind. This has sometimes been called vitality, or life; but it may save us from some ambiguity, if we employ, instead, the term organization, understanding by that expression that property which is found alike in animals and plants, but which is not found in the minerals and other substances of which the mass of the earth is composed.

The two distinguishing characteristics of organization are assimilation and reproduction.

The first of these characteristics is that power by which a plant, or animal, attracts to itself a portion of the nourishment which it receives, effects a change upon its nature, and forms it into organs, that is to say, into parts of the plant or animal, which are intended to subserve some further purpose. Every member of the organized creation selects from its appropriate sources of nourishment the elements necessary for its sustenance and increase. The matters thus selected are absorbed into the body of the plant or animal, and having been subjected to various changes, while they circulate in the veins and vessels with which all organized beings are stored, are either united to the plant or animal through which they pass, and of which they afterwards form a part, or are thrown off as excrementitious and unnecessary.

This characteristic of assimilation is altogether different from the attractions of crystallization and chemical affinity which we find in the inanimate substances of which the earth is chiefly composed. When crystallization, for instance, exerts its powers, whether in the processes of Art or of Nature, a great variety of beautiful forms are produced, which strive, as it were, to rival the wonders of the vegetable world. A piece of zinc, suspended in a solution of acetate of lead, is speedily surrounded by a cluster of crystals, which so closely resembles the product of vegetation, that it has been very appropriately termed the "leaden tree." The nitrate of silver sometimes deposits a mimic sprig of the precious metal; and the hoar-frost that whitens our fields, and covers our windows with its glittering incrustations, affords a still more striking illustration of the varied figures that crystallization produces. But in all these beautiful productions there is no assimilation of the substance attracted, and no formation of any part destined to subserve a farther end.

Reproduction, the other characteristic of organization, is that power by which new individuals are produced, by which the herb "yieldeth seed after his kind," and the animal gives birth to an offspring which bears the likeness and partakes of the nature of the parent from which it springs. Assimilation is the appointed means by which the preservation and perfection of the individual are secured; reproduction has for its object the multiplication of individuals and the perpetuation of the species.

The nature of these peculiar properties of organization, and the consequences resulting from them, present a very wide and interesting field for research, and, though many admirable works have been published on the subject, there is ample room for a multitude of future inquirers.

We shall briefly advert to a few particulars, in order to illus­trate the nature and characteristics of organization:—

Germination and Growth of Vegetables.—If we examine a seed, as, for example, that of wheat, or any of the other cereal plants, we usually find enclosed in its outer husk a quantity of farinaceous matter, destined for the nourishment of the future plant in the earlier stages of its existence. In this farina there is embedded a little speck which contains the principle of vegetable life. This little speck, usually termed the embryo or germ, sometimes exhibits even in the seed the rudiments of those parts of the infant plant which are first developed, but this is not always the case. When warmth and moisture are applied to a seed, in which the vegetative principle is entire, a chemical change is produced on the substance that surrounds the embryo, and the starchy matter which the seed originally contained is converted into a sweet and pulpy mass. If the life of the embryo has been destroyed, this change does not take place, the seed in that case either remains unaltered in its composition, or is subjected to the ordinary decay of putrefaction. Nature has thus given to the germ the power of preparing for itself the food that is suited for nourishing its after-growth. When the microscope is employed to enable the observer to trace the progress of germination, he discovers affixed to the different parts of the embryo a number of vesicles, or small cells, which have been formed out of the sweet mucilaginous fluid into which the farina was transformed. These vesicles are the materials out of which the various parts of the plant are afterwards produced: some adhere to the lower side of the germ and form the radicle, or nascent root; others are affixed to the upper side, and constitute the plumule, or infant stein. By degrees new vesicles are produced and attached to the embryo, and the parts continue to enlarge till the nourishment originally contained in the seed is exhausted. The root then begins to perform its appropriate office. It draws up moisture from the soil, and absorbs, along with the liquid, a variety of different substances, out of which new cells are formed and applied to the increase of the plant. For a time, no change in the formative process is observable,—the whole plant seems to consist of a congeries of cells; and in some classes of vegetables this cellular tissue, as it has been called, constitutes the whole, even of the perfected plant; but, in general, a gradual change is remarked. Vessels of a tubular form make their appearance. Some seem to be merely elongated cells, while others suggest the idea of a number of perfo­rated cells joined together. These are afterwards enlarged, changed in their form, and multiplied, till we find at last that wonderful collection of vessels, fibres, and tissues, which constitute the full-grown plant.

From the minuteness of the vessels thus formed, and the difficulty of examining into the circulation of living plants, it is not easy to determine the course that is taken either by the ascending or the descending fluids. It appears, however, in those plants which have been most carefully examined, that "the fluid matter in the soil, containing different substances in solution, is absorbed by the extremities of the roots, ascends to the stem, passes through the woody tissue, porous vessels, and cells, dissolving and appropriating various new substances. Proceeding upwards and outwards, the sap reaches the leaves and the bark, where it is exposed to the air and to the action of light, and is elaborated by the function of respiration. It then returns and descends chiefly through the bark, either directly or in a circuitous manner, communicating with the central parts by the medullary rays, depositing various secretions, more especially in the bark, and giving origin to substances which are destined to nourish and form new tissues. Finally, it reaches the extremity of the root where absorption commenced, a small portion is there excreted, while the remainder mixes with the newly-absorbed fluids, and again circulates in the sap."* The statement here quoted gives in clear and simple terms the conclusions to which physiologists generally have arrived. Without dwelling, however, on the nature of tissue or tubes, we have here sufficient evidence to shew us the wonderful power the great Creator has bestowed on the vegetative principle, or whatever term we may employ to designate the life of the plant. When the seed begins to spring, we find that the embryo in the first place effects a change upon the farinaceous matter which surrounds it and then collects from the nourishment thus prepared those particles of which the various members of the plant are afterwards formed. When this supply begins to fail, the rootlets imbibe, through the little sponges in which their extremities terminate, the aliment necessary for the growing herb. Every plant, if left in its natural state, takes in those matters that are necessary for its growth and vigour, while those that are unsuitable are left behind. Every plant, along with the carbonaceous matter which forms the principal part of its substance, and which is found abundantly dissolved in the soil, absorbs also the definite portion of lime or soda, potash, phosphorus, or silex, which its nature requires. The rootlets must, therefore, be regarded as having at least the power of selection, while some observations would lead us to conclude that they exert on the surrounding soil a chemical action, like that of the germ on the farina in which it is embedded. Be this as it may, they have the power of collecting from the soil the food necessary for their support. The matter thus absorbed, after undergoing various changes, especially in the leaves, is diffused through the plant; part of it goes to strengthen and increase the stem; part to form branches, leaves, and flowers; and yet another part, deposited in appropriate cells, constitutes the vast variety of chemical products which give to every member of the vegetable kingdom its peculiar taste, and smell, and medicinal powers. These products are so numerous that science can scarcely enumerate them; they are so varied in their properties, that we find them abundantly in every class of the chemist's nomenclature; they are so delicate in their composition, that few of them can be imitated by human art; yet all are originally derived from the same soil, and all are eliminated by the same agency—the influence of the sun and air;—the stinging nettle and the fragrant rose grow together, and the tree that bears the most luscious fruit intermingles its roots with those of the poisonous herb. The plant that we trample under foot, insignificant as it may appear, exhibits, in the mechanical arrangements of its varied parts, a delicacy of texture which the skill of the mechanician would vainly endeavour to imitate; and, in its microscopic laboratory, it effects combinations which the chemist, with all his art, cannot produce, and successfully carries on processes which man with all his science cannot understand.

Reproductive Power of Vegetables.—Wonderful as are the effects of assimilation in vegetables, their reproductive power is calculated to excite equal, if not greater, admiration. On examining the structure of plants, we find the greatest skill lavished upon the apparatus designed for producing and perfecting the seed. It is in the flower, where the vitality of the seed originates, that we discover the vegetable fabrics of fairest hue and finest texture. Nothing can be more delicate than the anther trembling on its slender thread; nothing more beautiful than the corolla opening its petals to the orb of day. "Consider the lilies how they grow, they toil not, neither do they spin; and yet Solomon in all his glory was not arrayed like one of these." And while the beauty of their form, and the brightness of their varied hues, make the parts connected with the fructification peculiarly attractive to the eye, the great design for which the flower has been formed deserves more especial remark. It is the instrument, or apparatus, by which the Creator secures the perpetuity of the species. The flower produces seed, and the seed when sown, produces a plant partaking in all essential particulars of the nature of the parent to which it owes its origin. Such is the law given to the vegetable world, and that law we find most implicitly obeyed. Some perhaps might at first be inclined to consider the varieties produced by cultivation as exceptions to this general statement; we must, however, keep in mind that these varieties are in fact accidental monstrosities, which require all the art and care of man to preserve. If left to the ordinary course of nature, artificial varieties will either perish without producing fruit at all, or, if they bear seed, the plants that spring from it will, in each succeeding generation, bear a closer and closer resemblance to the original type from which they were derived. All varieties, moreover, are but varieties of form; the essential character of the plant remains unchanged.

We can assign no reason why this should be the case, why the oak should always produce an oak, or the rose a rose. We see that this is the established order of nature; we see no instance of any species being transformed into another. A moment's reflection is sufficient to shew us many beneficial consequences resulting from this determinate arrangement; but, beyond this we cannot go. It might have been ordered, as some dreamers have fancied, that the sea-weed gradually changed into the flowering herb, and the herb into a tree; but had it been so appointed, we could never have had any confidence in Nature's arrangements, and man, and all the other creatures that are nourished by the produce of the field, must soon have perished from lack of appropriate sustenance.

Embryo condition of Animals.—In describing the nature of vegetable organization, we traced the progress of the germ, as it gradually develops its powers, and expands into the full-grown herb: we shall follow a similar course in considering the nature and results of the corresponding principle in animals.

When we examine the egg of a bird, we find that it consists of two parts; the yolk, which we may call the original and essential portion, and the albuminous covering that surrounds it; but no trace of the future bird can be discovered. After the egg has been kept at a suitable temperature for a little time, the germ appears in the form of a small speck near one end. The requisite warmth being continued, the more important members of the animal assume, one after another, their appropriate form and position; and this process goes on till the nestling, fitted for breathing the air, and for receiving nourishment by the mouth, bursts the shell, and leaves the prison in which it had been confined. A precisely similar process may be observed in the spawn of fishes, and eggs of serpents, tortoises, and lizards. In the class of mammalia, the ovum, or egg, is attached to the womb of the mother, and the foetus does not derive its nourishment from the fluid that surrounds it, but from the blood of the parent, which, by a wise provision of the Creator, is made to circulate through its veins. In this case however, as in the others, the embryo has the power of assimilating to itself the nourishment provided for it. It first exists as a microscopical speck, the various members are gradually developed, and the size continues to increase, till it leaves the womb, and enters on its new state of existence. This process is so exactly similar to that which takes place in the germination of seeds, that we cannot hesitate in classing them together.

Nourishment of Animals.—After the bird has burst the shell, and the mammal has left the womb, the process of digestion carried on in the stomach bears an evident resemblance to the chemical changes which are effected by the springing germ on the farina of the surrounding seed, and to that power by which the roots of growing vegetables are enabled, in some cases, to produce a change in the substances around them. The lacteal tubes, that collect from the stomach and entrails the nourishment eliminated from the digested food, may, in like manner, be compared to the rootlets of plants, with their terminating spongioles, absorbing from the soil the sap with the nourishment that it holds in solution.

Beyond these few particulars, however, the points of difference between the animal and the vegetable organization become more remarkable than those of resemblance. We find, for instance, that while plants are nourished by external means, animals must feed themselves. The appropriate aliment on which the life of the vegetable depends is either originally contained in the earth in which it grows, or is brought to it by the falling shower. The case is very different with respect to the animal creation. The living creature must go forth in quest of its food, and, in many cases, it is only after lengthened search and protracted toil that it finds the means of sustaining its health and strength. Even those creatures that form a kind of intermediate link between the animal and the plant, the sponges and kindred tribes, though fixed immovably to the places where their existence began, collect by their own exertion the nourishment on which they live. The algae, and other aquatic vegetables, have their sustenance brought to them by the currents which external causes produce; but the zoophyte originates the movement of the water which brings home to it its food.

However cursory the glance may be which we take of the subject before us, we cannot avoid remarking how wonderfully the various circumstances on which the nourishment of animals depends are adapted to each other in every individual case. Every animal has certain peculiarities which render it necessary that it should be supplied with its appropriate food;—the lion could not live on grass, nor the ox on the flesh of the slain; that food, therefore, must be provided. But this is not all; there must be implanted in the animal an appetite and taste to induce it to seek and select its destined nourishment; there must be external organs fitted for procuring the needed supply; there must be teeth or other instruments to prepare it for the stomach, and a stomach capable of digesting the aliment supplied. And all these circumstances we find concurring in. regard to every one of the many thousand species of animals that people the globe, and in regard to every one of the many millions of individuals which these species include. Every one has organs and appetites adapted to the food that is destined for its use; for every one there is food provided, and that food is provided in such a climate, and in such a situation, as is suited to the animal's power of enduring heat and cold, and to all the varied circumstances of its nature!

Reproduction of Animals.—In no respect do we find the difference between the economy of the vegetable and that of the animal more remarkable than in regard to the arrangements by which the species is propagated and preserved. In either case, however, the offspring partakes of the nature of the parent from which its being is derived; though the means by which the species are preserved are widely different. In plants the reproductive organs which originate the seed, either grow together on the same stem, or are made to influence each other through the instrumentality of the currents of air with which they are surrounded. But among animals the male and female are altogether distinct; though helpmates meet for each other, they are different creatures, they have separate sources of nourishment, they generally differ in character, and sometimes are so unlike in appearance and shape, that they might at first be regarded as belonging to distinct divisions of the animal kingdom. Their union, therefore, must be effected by an arrangement totally dif­ferent from that which suffices in regard to the vegetable creation. Appetites and desires have accordingly been implanted in them, to which there is nothing corresponding in the plant, by which they are led to provide for the continuance of the species, and for the preservation of their offspring, while blindly seeking the gratification of the instincts that have been implanted within them.

Organization of Man.—In examining the organization of man, we find no essential difference between him and the creatures around him. From the commencement of his earthly existence to its close, he is nourished and preserved by a variety of processes precisely similar to those which we discover in the other inhabitants of the globe.

At the same time, nothing can be more wonderful than the varied organization by which the functions of animal life are carried on. The various chemical changes which the food under goes in passing through the body, till the nutritious part is absorbed, and the residuum rejected,—the operation of the heart, with its perpetual motion, causing the blood to perform its unceasing circuit,—the action of the various glands, and the inter­nal organs, with their peculiar secretions and uses,—the delicate network of the nerves, and the part assigned to them in the animal economy,—the system of absorption and reproduction,—that vis medicatrix naturæ, by which the whole frame undergoes a perpetual process of renewal, and accidental injuries are healed,—all the parts of our frame, in short, are full of wonders;—their number and variety pass our power of computation, their ex­treme delicacy defies the power of microscopical investigation fully to describe them,—yet so admirably are they all adjusted, that, from day to day, the complicated and delicate machinery performs its appropriate functions, till accident or disease causes it prematurely to cease, or, its destined term having been fulfilled, natural decay gradually checks its motion and lays it to rest in death.

"Strange, that a harp of such unnumber'd strings
Should keep in tune so long!"

Imperfect as is the sketch which our limits permit us to give of the nature of organization, it is abundantly evident that its characteristics are altogether different from the general properties of matter which we before described, and from the effects of the imponderable agents. Some have conjectured that life is but a modification of electricity; others have supposed that the digestive power of the stomach is merely an effect of galvanic action; but nothing can be more absurd than such suppositions. These subtile agents may be made the means of stimulating functions that formerly existed, though it may be in a dormant state; but, whatever effects may have been produced on organic substances by their application, we have no evidence whatever of their originally producing either growth or vitality. All the imponderable agents, heat, light, electricity, and galvanism, have a powerful effect in stimulating the functions of animal and vegetable life, but they are not life; they are merely the means by which the vital energies may be excited. We see nothing in the effects which they produce, when unconnected with organic vitality, that bears any resemblance to assimilation or reproduction—the characteristics that distinguish organization; and the more carefully we investigate the subject, the more evidently does it appear, that organization is a power of a higher order, though it acts in a more limited sphere, and that its products exhibit more wonderful proofs of a Creator's skill, though they are on a smaller scale, and of a more fragile kind.