“For hot, cold, moist, and dry, four champions fierce,
Strive there for mast'ry, and to battle bring
Their embryon atoms,—”
but rather as one vast homogeneous fluid, and even that he suggests not as a historical fact, but as the appropriate symbol of a great fundamental truth. The first effort of magnetic power, the first step from indifference to difference, from formless homogeneity to independent existence, is seen in the tranquil deposition of crystals; and an increasing tendency to difference is observable in the increasing multitude of strata, till we come to organic life; of which the vegetable and animal worlds may be regarded as opposite poles; carbon prevailing in the former and azote in the latter; and vegetation being characterised by the predominance of magnetism in its highest power, as reproduction; whilst the animal tribes evince the power of electricity, as shown in irritability and sensibility. Passing over the forms of vegetation, we come to the polypi, corallines, &c., in which individuality appears in its first dawn; for a multitude of animals form, as it were, a common animal, and different genera pass into each other, almost indistinguishably. The tubipora of the corals connects with the serpula of the conchylia. In the mollusca the separation of organs becomes more observable; in the higher species there are rudiments of nerves, and an exponent, though scarcely distinguishable, of sensibility. In the snail, and muscle, the separation of the fluid from the solid is more marked, yet the prevalence of the carbonic principle connects these and the preceding classes, in a certain degree, with the vegetable creation. “But the insect world, taken at large (says Mr. Coleridge) appears as an intense Life, that has struggled itself loose, and become emancipated from vegetation—Floræ liberti, et libertini!” In insects we first find the distinct commencement of a separation between the muscular system, that is, organs of irritability, and the nervous system, that is, organs of sensibility; the former, however, maintaining a pre-eminence throughout, and the nerves themselves being probably subservient to the motory power. With the fishes begins an internal system of bones, but these are the results of a comparatively imperfect formation, being in general little more than mere gristle. In birds we find a sort of synthesis of the powers of fish and insects. In all three, the powers are under the predominance of irritability; but sensibility, which is dormant in the insect, begins to awaken in the fish, and, though still subordinate, is quite awake in the bird, of which no better proof can be given than its power of sound, with the rudiments of modulation, in the large class of singing birds, and in some others a tendency to acquire and to imitate articulate speech. The next step of ascent brings us to the mammalia; and in these, including beasts and men, the complete and universal presence of a nervous system raises sensibility to its due place and rank among the animal powers. Finally, in Man the whole force of organic power attains an inward and centripetal direction, and the “apex of the living pyramid”becomes a fit receptacle for Reason and Conscience.
It is much to be regretted, that the estimable Author did not live to put a finishing hand to this Essay; but the part completed involves speculations of so interesting a nature, and presents such striking marks of deep and original thought, that the Editor, to whose hands it was committed, did not feel himself justified in withholding it from the judgment of the public.
Physiology Of Life.
Introduction
When we stand before the bust of John Hunter, or as we enter the magnificent museum furnished by his labours, and pass slowly, with meditative observation, through this august temple, which the genius of one great man has raised and dedicated to the wisdom and uniform working of the Creator, we perceive at every step the guidance, we had almost said, the inspiration, of those profound ideas concerning Life, which dawn upon us, indeed, through his written works, but which he has here presented to us in a more perfect language than that of words—the language of God himself, as uttered by Nature.
That the true idea of Life existed in the mind of John Hunter I do not entertain the least doubt; but it may, perhaps, be doubted whether his incessant occupation, and his stupendous industry in the service, both of his contemporaries and of posterity, added to his comparatively slight acquaintance with the arts and aids of logical arrangement, permitted him fully to unfold and arrange it in distinct, clear, and communicable conceptions. Assuredly, however, I may, without incurring the charge of arrogance or detraction, venture to assert that, in his writings the light which occasionally flashes upon us seems at other times, and more frequently, to struggle through an unfriendly medium, and even sometimes to suffer a temporary occultation. At least, in order to dissipate the undeniable obscurities, and to reconcile the apparent contradictions found in his works,—to distinguish, in short, the numerous passages in which without, perhaps, losing sight internally of his own peculiar belief, he yet falls into the phraseology and mechanical solutions of his age,—we must distinguish such passages from those in which the form corresponds to the substance, and in which, therefore, the nature and essential laws of vital action are expressed, as far as his researches had unveiled them to his own mind, without disguise. To effect this, we must, as it were, climb up on his shoulders, and look at the same objects in a distincter form, because seen from the more commanding point of view furnished by himself. This has, indeed, been more than once attempted already, and, in one instance, with so evident a display of power and insight as announces in the assertor and vindicator of the Hunterian Theory a congenial intellect, and a disciple in whom Hunter himself would have exulted. Would that this attempt had been made on a larger scale, that the writer to whom I refer1 had in consequence developed his opinions systematically, and carried them yet further back, even to their ultimate principle!
But this the scientific world has yet to expect; or it is more than probable that the present humble endeavour would have been superseded, or confined, at least, to the task of restating the opinion of my predecessor with such modifications as the differences that will always exist between men who have thought independently, and each for himself, have never failed to introduce, even on problems of far easier and more obvious solution.
Without further preface or apology, therefore, I shall state at once my objections to all the definitions that have hitherto been given of Life, as meaning too much or too little, with an exception, however, in favour of those which mean nothing at all; and even these last must, in certain cases, receive an honour they do not merit, and be confuted, or rather detected, on account of their too general acceptance, and the incalculable power of words over the minds of men in proportion to the remoteness of the subject from the cognizance of the senses.
It would be equally presumptuous and unreasonable should I, with a late writer on this subject, “exhort the reader to be particularly on his guard against loose and indefinite expressions;” but I perfectly agree that they are the bane of all science, and have been remarkably injurious in the different departments of physiology.
The Nature Of Life.
On The Definitions Of Life Hitherto Received. Hints Towards A More Comprehensive Theory
The