Pagina-afbeeldingen
PDF
ePub

only of being secure, but of being out of the way; which it would hardly have been in any position that could be assigned to it in the anterior part of the orb, where its function lies. When the muscle behind the eye contracts, the membrane, by means of the communicating thread, is instantly drawn over the forepart of it. When the muscular contraction (which is a positive, and, most probably, a voluntary effort,) ceases to be exerted, the elasticcity alone of the membrane brings it back again to its position*. Does not this, if any thing can do it, bespeak an artist, master of his work, acquainted with his materials ?" Of a thoufand other things," fay the French Academicians, "we perceive not the contrivance, because we understand them only by the effects, of which we know not the causes; but we here treat of a machine, all the parts whereof are visible; and which need only be looked upon to discover the reasons of its motion and action f." J

* Phil. Trans. 1796.

t Memoirs for a Natural History of Animals by the Royal Academy of Sciences at Paris, done into English by Order of the Royal Society, 1701, p. 249.

In the configuration of the muscle, which, though placed behind the eye, draws rhe nictitating membrane over the eye, there is, what the authors, just now quoted, deservedly call a marvellous mechanism. I suppose this structure to be found in other animals; but, in the Memoirs from which this account is taken, it is anatomically demonstrated only in the cassowary. The muscle is fajsed through a loop formed by another muscle; ai;d is there inflected, as if it wtre round a pulley. This is a peculiarity; and observe the advantage of it. A single muscle with a straight tendon, which is the common muscular form, would have beeti sufficient, if it had had power to draw far enough. But the contraction, necessary to draw the membrane over the whole eye, required a longer muscle than could lie straight at the bottom of the eye. Therefore, in order to have a greater length in a less compass, the cord of the main muscle makes an angle. This, so far, answered the end; but, still further, it makes an angle, not round a fixed pivot? but round a loop formed by another muscle; which second muscle, whenever it contracts, of course twitches the first muscle

at at the point of inflection, and thereby assists the action designed by both.

One question may possibly have dwelt in the reader's mind during the perufal of these observations, namely, Why should not the Deity have given to the animal the faculty of vision Mi once? Why this circuitous perception; the ministry of so many means? an element provided for the purpose; reflected from opaque substances, refracted through transparent ones; and both according to precise laws: then, a complex organ, an intricate and artificial apparatus, in order, by the operation of this element, and in conformity with the restrictions of these laws, to produce an image upon a membrane communicati g with the brain? Wherefore all this? Why make the difficulty in order only to surmount it? If to perceive objects by some other mode than that of touch, or objects which lay out of the reach of that sense, were the thing purposed, could not a simple volition of the Creator have communicated the capacity? Why resort to contrivance, where power is omnipotent? Contrivance, by its very definition and nature,

is is the refuge of impersection. To have recourse to expedients, implies difficulty, impediment, restraint, defect of power. This question belongs to the other senses, as well as to fight; to the general functions of animal life, as nutrition, secretion, respiration; to the economy of vegetables; and indeed to almost all the operations of nature. The question therefore is of very wide extent; and, amongst other answers, which may be given to it, beside reasons of which probably we are ignorant, one answer is this. It is only by the display of contrivance, that the existence, the agency, the wisdom of the Deity, could be testified to his rational creatures. This is the scale by which we ascend to all the knowledge of our Creator which we possess, so far as it depends upon the phænomena, or the works of nature. Take away this, and you take away from us every subject of observation, and ground of reasoning; I mean as our rational faculties are formed at present. Whatever is done, God could have done, without the intervention of instruments or means: but it is in the construct on of instruments, in the choice and adaptation of means, that a creative intelligence is seen, it is this which constitutes the order

and and beauty of the universe, God, therefore, has been pleased to prescribe limits to his own power, and to work his ends within those limits. The general laws of matter have perhaps the nature of these limits; its inertia, its reaction; the laws which govern the communication of motion, the refraction and reflection of light, the constitution of fluids non-elastic and elastic, the transmission of sound through the latter; the laws of magnetism, of electricity; and probably others yet undiscovered. These are general laws; and when a particular purpose is to be effected, it is not by making a new law, nor by the suspension of the old ones, nor by making them wind and bend and yield to the occasion (for nature with great steadiness adheres to, and supports them), but it is, as we have seen in the eye, by the interposition of an apparatus corresponding with these laws, and suited to the exigency which results from them, that the purpose is at length attained. As we have faid, therefore, God prescribes limits to his power, that he may let in the exercise, and thereby exhibit demonstrations of his wisdom. For then, i. e. such laws and limitations being laid down, it is as though one Being should have fixed certain rules;

and,

« VorigeDoorgaan »