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OF THE MECHANICAL AND IMMECHANICAL PARTS AND FUNCTIONS at ANIMALS AND VEGETABLES.'
It is not that every past of an animal of vegetable has not proceeded from a contriving mind; or that every patt is not constructed with a view to its proper end and purposes according to the laws belonging to, and governing, the substance or the action made use of in that part; or that each part is not so constructed, as to effectuate its purpose whilst it operates according to these laws : but it is, because these laws themselves are not in all cases equally understood; or, what amounts to nearly the fame thing, are not equally exemplified in more simple processes, and more simple machines; that we lay down the distinction, here proposed, between the mechanical parts, and other parts, of animals and vegetables.
For instance; the principle of muscular motion, viz. upon what cause the swelling of the belly of the muscle, and consequent
contraction contraction of its tendons, either by an act of the will or by involuntary irritation, depends, is wholly unknown to us. The substance employed, whether it be fluid, gaseous, elastic, electrical, or none of these, or nothing res mbling these, is also unknown to us: of course, the laws belonging to that substance, and which regulate its action, are unknown to us. We see nothing similar to this contraction in any machine which we can make, or any process which we can execute. So far (it is conferred) we are in ignorance: but no further. This power and principle, from whatever cause it proceeds, being assumed, the collocation of the fibres to receive the principle, the disposition of the muscles for the use and application of the power, is mechanical; and is as intelligible as the adjustment of the wires and strings by which a puppet is moved. We feel therefore, as far as respects the subject before us, what is not mechanical in the animal frame, and what is. The nervous influr ence (for we are often obliged to give names to things which we know little about)—I fay the nervous influence, by which the belly or middle of the muscle is swelled, is not mechanical. The utility of the effect we perceive;
G 3 the the means, or the preparation of means, by which it is produced, we do not. But obscurity as to the origin of muscular motion brings no doubtfulness into our observations upon the sequel of the process. Which observations relate, sit, to the constitution of the muscle; in consequence of which constitution, the swelling of the belly or middle part is necessarily and mechanically followed by a contraction of the tendons: 2dly, to the number and variety of the muscles, and the corresponding number and variety of useful powers which they supply to the animal; which is astonishingly great: 3dly, to the judicious (if we may be permitted to use that term, in speaking of the author, or of the works, of nature), to the wise and well contrived disposition of each muscle for its specific purpose ; for moving the joint this way, and that way, and the other way; for pulling and drawing the part, to which it is attached, in a determinare and particular direction; which is a mechanical operation, exemplified in a multitude of instances. To mention only one; the tendon of the trochlear muscle of the eye, to the end that it may draw in the line required, is passed through a cartilaginous ring, at which
it is reverted, exactly in the fame manner as a rope in a ship is carried over a block or round a stay, in order to make it pull in the direction which is wanted. All this, as we have faid, is mechanical; and is as accessible to inspection, as capable of being ascertained, as the mechanism of the automaton in the Strand. Suppose the automaton to be put in motion by a magnet (which is probable), it will supply us with a comparison very apt for our present purpose. Of the magnetic effluvium we know perhaps as little as we do of the nervous fluid. But magnetic attraction being assumed (it signifies nothing from what cause it proceeds), we can trace, or there can be pointed out to us, with perfect clearness and certainty, the mechanism, viz. the steel bars, the wheels, the joints, the wires, by which the motion so much admired is communicated to the fingers of the image: and to make any obscurity or difficulty, or contraversy in the doctrine of magnetism, an objection to our knowledge or our certainty concerning the .contrivance, or the marks of contrivance, displayed in the automaton, would be exactly the fame thing, as it is to make our ignorance (which we acknowledge) of the G 4 cause
cause of nervous agency, or even of the substance and structure of the nerves themselves, a ground of question or suspicion as to the reasoning which we institute concerning the mechanical part of our frame. That an animal is a machine, is a proposition neither correctly true, nor wholly false. The distinction which we have been discussing will serve to shew how far the comparison, which this expression implies, holds; and wherein it fails. And, whether the distinction be thought of importance or not, it is certainly of importance to remember, that there is neither truth nor justice in endeavouring to bring a cloud over our understandings, or a distrust into our reasonings upon this subject, by suggesting that we know nothing of voluntary motion, of irritability, of the principle of life, of senfation, of animal heat, upon all which the animal functions depend; for our ignorance of these parts of the animal frame concerns not at all our knowledge of the mechanical parts of the fame frame. I contend, therefore, that there is mechanism in animals; that this mechanism is as properly such,as it is in machines made by art; that this mechanism is intelligible and certain; that it is not the less so