provisions for its moving over ground. But if, anticipating the metamorphosis, we dissected the same larva immediately before the change, we should find a new apparatus in progress towards perfection; we should see the muscles of its many feet decaying; the nerves to each muscle wasting; a new arrangement of muscles, with new points of attachment, directed to the wings, instead of to the feet; and finally, a new distribution of nerves, accommodated to the members about to be put in motion. Here is no budding or stretching forth of organs, under the influence of surrounding elements; it is a change operated on all the economy, and prospective, that is, in anticipation of a condition which the creature has not yet attained.

These facts countenance the conclusion drawn from the comparative anatomy of the hand and arm—that with each new instrument, visible externally, there are a thousand internal relations established. The introduction of a new mechanical contrivance in the bones or joints, infers an alteration in every part of the skeleton; a corresponding arrangement of all the muscles; an appropriate distribution of the nervous filaments laid intermediate between the instrument and the centre of life and motion; and finally, in relation to the new organ, new sources of activity must be created, otherwise the part will hang an useless appendage.

It must now be apparent, that nothing less than the Power which originally created, is equal to effect those changes on animals, which adapt them to their conditions: and that their organisation is predetermined; not consequent on the condition of the earth or of the surrounding elements. Neither can a property in the animal itself account for the changes which take place in the individual, any more than it can for the varieties in the species. Every thing declares the diversity of species to have its origin in distinct creations; and not to be owing to a process of gradual transition from some original type. Any other hypothesis than that of new creations of animals, suited to the successive changes in the inorganic matter of the globe-the condition of the water, atmosphere, and temperature-brings with it only an accumulation of difficulties.

To fortify what we have said, we ought not to omit bringing into the argument a series of changes of structure altogether

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differing from those which we have been hitherto considering revolutions in the material of the frame, which take place, without a pause, and during the whole life, in every animal. From no study of the mechanical adaptations of the body, not even from examining the structure and endowments of the organs of the senses, can we obtain a higher idea of the Power which continually superintends the processes of the economy, than from viewing the influence of life, in collecting, arranging, and incessantly changing the material of the animal frame. Astounded by the magnitude of natural objects, bewildered by seeing neither beginning nor end, beholding processes of decay alone, persuaded, almost, that everything must be yielded up to a power of destruction,-how useful is it to possess proofs, in the microcosm of the living body, that even when the substance of which that body is composed, is undergoing a ceaseless change, to its minutest elements, the whole animal system may continue in freshness and vigour ?

[Is it not surprising that an individual, who retains every peculiarity of body and of mind, whose features, whose gait and mode of action, whose voice, gestures, and complexion we are ready to attest as the very proof of personality, should, in the course of a few days, change every particle of his solid fabric; that he, whom we suppose we saw, is, so far as his body is concerned, a perfectly different person from him we now see! That the fluids may change, we are ready to allow; but that the solids should be thus ever shifting, seems at first improbable. And yet, if there be anything firmly established in physiology, if there be truth in the science at all, that fact is incontrovertible.

There is nothing like this in inanimate nature. It is beautiful to see the shooting of a crystal; to note the formation of the integrant particles from their elements in solution, and these, under the influence of attraction or crystalline polarity, assuming a determinate shape; but the form here is permanent. In the different processes of elective attraction, and in fermentation, we perceive a commotion; but in a little time the products are formed, and the particles are at rest. In these instances there is nothing like the revolutions of the living animal substance, where the material is alternately arranged, decomposed, and re-arranged.

The end of this is, that the machinery of the body is ever new; that it possesses a property within itself of mending that which was broken, of throwing off that which was useless, of building up that which was insecure and weak, of repelling disease, or of controlling it, and of substituting what is healthful for that which is morbid. The whole animal machinery we have seen to be fragile and liable to injury; now, without this continual change of material, and this new modelling of that material, our lives would be precarious; the texture of our bodies would be spoiled; like some fine piece of mechanism which had stopped, and which no workman had knowledge sufficient to reconstruct. By these living actions the minute particles of the body die successively; not as in the final death of the whole body; but part by part is deprived of vitality, and taken into the general circulation, in order to be cast out of the system; whilst new parts received from the food are endowed with life, and built up in their place. Thus we see that nature, instead of having to establish a new mode of action for every casualty, heals all wounds, unites all broken bones, throws off all morbid parts, by the continuance of its usual operations; and the surgeon, who is modest in his calling, has nothing to do but to watch, lest ignorance or prejudice interfere with the process of nature. This property of the living body to restore itself when deranged, or to heal itself when broken or torn, is an action which so frequently assumes the appearance of reason, as if it were adapting itself to the particular occasion, that Mr John Hunter speaks of parts of the body as "conscious of their imperfection," and "acting from the stimulus of necessity;" thus giving the properties of mind to the body, as the only explanation of phenomena so wonderful.

The bones of the leg and thigh, which suffer the fatigue of motion, and support the weight of the body, are nevertheless continually undergoing an operation of repair; in which the old particles are withdrawn, whilst new ones replace them, without in the slightest measurable degree diminishing their length, or altering their proper form. We see with what care the walls of a house are shored up, to admit of repair-how correctly the workman must estimate the strength of his pillars and beams-how nicely he must hammer in his wedges, that

every interstice may be filled, and no strain be permitted; and if this operation fail in the slightest degree, it is attended with a rent in the wall from top to bottom. We say, then, that from the very awkwardness of this proceeding, (in which, after all, there is danger of the whole fabric tumbling about the workmen,) we are called upon to admire how the solid pillars in our own frames are a thousand times renewed, whilst the plan of the original fabric is followed, to the utmost nicety, in their restoration. And if it deviate at all, it is only in a manner to surprise us the more since it will be discovered that the change has been effected with a view to adapt the strength of material to some new circumstance; as the increasing weight which the bone has to support, or the jar it is subject to, from some alteration in the activity or exercise of the body.

There is a living principle, which, while the material changes, is itself permanent; attracting and arranging, dissolving and throwing off successive portions of the solids. And, influencing this living principle, there is a law which shapes, and limits the growth of, every part; and carries it through a regular series of changes, in which its form and aptness for its office are preserved, whilst the material alone is altered. The influence of disease will, for a time, disorder this modelling process, and produce tumours and distortions; but when at length the healthy action-that is, the natural action-prevails, these incumbrances are carried away, and the fair proportions of the fabric are restored.]

Life preserves the materials of the body free from the influence of those affinities which hold the inorganic world together; and it not only does that, but it substitutes other laws. Of the wonders of the microscope, none exceed those presented on looking at the early rudiments of an animal-it may be of the largest creature that inhabits the earth. This rudimentary structure will but appear an homogeneous, transparent, soft jelly; there will be visible in it only a single pulsating point; yet this mass possesses within it a principle of life; and it is not only ordered what this influence shall perform in attracting matter, and building up the complex structure of the body, but even the duration of the animal's existence is from the beginning defined. The term may be limited to a day, and the life be truly ephemeral; or it may be prolonged to a hundred years;

but the period is adjusted according to the condition and enjoyment of the individual, and to the continuance of its species, as perfectly as are the mechanism and structure themselves.

[In a seed, or a nut, or an egg, we know that there is life: from the length of time that these bodies will remain without development, we are forced to acknowledge that this life is stationary or dormant; and that it is limited to the counteraction of putrefaction or chemical decomposition. But no sooner does this living principle become active, than a series of intestinal or internal changes are commenced; which are regularly progressive, without a moment's interruption, while life continues. That principle, which may continue an indefinite number of days, months, or years, without producing any change, begins at once to exhibit its influence, builds up the individual body, regulates the actions of secretion and absorption; and, by its operation upon the material of the frame, stamps it with external marks of infancy, maturity, and age.

Those who say that life results from structure, and that the material is the ruling part, bid us look to the contrast of youth and age. The activity of limb and buoyancy of spirit in youth they consider as necessary consequences of the newness and perfection of the organisation. On the other hand, a ruined tower, unroofed, its walls exposed to be broken up by alternation of frost and heat, dryness and moisture, wedged by the roots of ivy, and toppling to its fall, they compare to old agewith the shrunk limbs, tottering gait, shrivelled face, and scattered grey hair of the old.

But in all this there is no truth. Whilst there are life and circulation, there is change of the material of the frame; and there is a sign of that if a broken bone unite, or a wound heal. Ascribe the distinction to the velocity of circulation, or to the more or less energy of action, or to the rapidity of change; but with the antiquity of the material, it can have nothing to do. The roundness and fulness of flesh, the smoothness, transparency, and colour of the cheek, belong to youth as characteristic of the time of life, not as a necessary quality of the material. Is there a physiognomy in all nature-among birds and beasts, insects and flowers-and shall man alone have no indication of his condition, in the outward form and character? The distinctions in the body apparent in the stages of life, have a