|March 22, 2012||Filled under All text of Paley Natural Theology, Chapter 14||
I can hardly imagine to myself a more distinguishing mark, and consequently a more certain proof of design, than preparation, i.e. the providing of things beforehand which are not to be used until a considerable time afterwards: for this implies a contemplation of the future, which belongs only to intelligence.
Of these prospective contrivances, the bodies of animals furnish various examples.
I. The human teeth afford an instance, not only of prospective contrivance, but of the completion of the contrivance being designedly suspended. [Pl. XXVIII. fig. 1 and 2.] They are formed within the gums, and there they stop; the fact being, that their farther advance to maturity would not only be useless to the new-born animal, but extremely in its way; as it is evident that the act of sucking, by which it is for sometime to be nourished, will be performed with more ease both to the nurse and to the infant, whilst the inside of the mouth, and edges of the gums, are smooth and soft, than if set with hard pointed bones. By the time they are wanted, the teeth are ready. They have been lodged within the gums for some months past, but detained as it were in their sockets, so long as their farther protrusion would interfere with the office to which the mouth is destined. Nature, namely, that intelligence which was employed in creation, looked beyond the first year of the infant’s life; yet, whilst she was providing for functions which were after that term to become necessary, was careful not to incommode those which preceded them. What renders it more probable that this is the effect of design, is, that the teeth are imperfect, whilst all other parte of the mouth are perfect. The lips are perfect, the tongue is perfect; the jaws, the palate, the pharynx, the larynx, are all perfect, the teeth alone are not so. This is the fact with respect to the human mouth: the fact also is, that the parts above enumerated are called into use from the beginning; whereas the teeth would be only so many obstacles and annoyances, if they were there. When a contrary order is necessary, a contrary order prevails. In the worm of the beetle, as hatched from the egg, the teeth are the first things which arrive at perfection. The insect begins to gnaw as soon as it escapes from the shell, thought its other parts be only gradually advancing to their maturity.
What has been observed of the teeth, is true of the horns of animals, and for the same reason. The horn of a calf or a lamb does not bud, or at least does not sprout to any considerable length, until the animal be capable of browsing upon its pasture; because such a substance upon the forehead of the young animal, would very much incommode the teat of the dam in the office of giving suck.
But in the case of the teeth, of the human teeth at least, the prospective contrivance looks still farther. A succession of crops is provided, and provided from the beginning; a second tier being originally formed beneath the first, which do not come into use till several years afterwards. And this double or suppletory provision meets a difficulty in the mechanism of the mouth, which would have appeared almost insurmountable. The expansion of the jaw (the consequence of the proportionable growth of the animal and of its skull,) necessarily separates the teeth of the first set, however compactly disposed, to a distance from one another, which would be very inconvenient. In due time, therefore, i.e. when the jaw has attained a great part of its dimensions, a new set of teeth springs up (loosening and pushing out the old ones before them,) more exactly fitted to the space which they are to occupy, and rising also in such close ranks, as to allow for any extension of line which the subsequent enlargement of the head may occasion.
II. It is not very easy to conceive a more evidently prospective contrivance than that which, in all viviparous animals, is found in the milk of the female parent. At the moment the young animal enters the world, there is its maintenance ready for it. The particulars to be remarked in this economy are neither few nor slight. We have, first, the nutritious quality of the fluid, unlike, in this respect every other excretion of the body; and in which nature hitherto remains unimitated, neither cookery nor chemistry having been able to make milk out of grass. We have, secondly, the organ for its reception and retention; we have, thirdly, the excretory duct, annexed to it; and we have, lastly, the determination of the milk to the breast, at the particular juncture when it is about to be wanted. We have all these properties in the subject before us; and they are all indications of design. The last circumstance is the strongest of any. If I had been to guess beforehand, I should have conjectured, that at the time when there was an extraordinary demand for nourishment in one part of the system, there would be the least likelihood of a redundancy to supply another part. The advanced pregnancy of the female has no intelligible tendency to fill the breast with milk. The lacteal system is a constant wonder; and it adds to other causes of our admiration, that the number of the teats and paps in each species is found to bear a proportion to the number of the young. In the sow, the bitch, the rabbit, the cat, the rat, which have numerous litters, the paps are numerous, and are disposed along the whole length of the belly: in the cow and mare they are few. The most simple account of this, is to refer it to a designing Creator.
But, in the argument before us, we are entitled to consider not only animal bodies when framed, but the circumstances under which they are framed: and in this view of the subject, the constitution of many of their parts is most strictly prospective.
III. The eye is of no use at the time when it is formed. It is an optical instrument made in a dungeon; constructed for the refraction of light to a focus, and perfect for its purpose, before a ray of light has had access to it; geometrically adapted to the properties and action of an element with which it has no communication. It is about indeed to enter into that communication; and this is precisely the thing which evidences intention. It is providing for the future in the closest sense which can be given to these terms; for it is providing for a future change, not for the then subsisting condition of the animal, not for any gradual progress or advance in that same condition, but for a new state, the consequence of a great and sudden alteration, which the animal is to undergo at its birth. Is it to be believed that the eye was formed, or, which is the same thing, that the series of causes was fixed by which the eye is formed, without a view to this change; without a prospect of that condition, in which its fabric, of no use at present, is about to be of the greatest; without a consideration of the qualities of that element, hitherto entirely excluded, but with which it was hereafter to hold so intimate a relation? A young man makes a pair of spectacles for himself against he grows old; for which spectacles he has no want or use whatever at the time he makes them. Could this be done without knowing and considering the defect of vision to which advanced age is subject? Would not the precise suitableness of the instrument to its purpose, of the remedy to the defect, of the convex lens to the flattened eye, establish the certainty of the conclusion, that the case, afterwards to arise, had been considered beforehand, speculated upon, provided for? all which are exclusively the acts of a reasoning mind. The eye formed in one state, for use only in another state, and in a different state, affords a proof no less clear of destination to a future purpose, and a proof proportionably stronger, as the machinery is more complicated, and the adaptation more exact.
IV. What has been said of the eye, holds equally true of the lungs. Composed of air-vessels, where there is no air; elaborately constructed for the alternate admission and expulsion of an elastic fluid, where no such fluid exists: this great organ, with the whole apparatus belonging to it, lies collapsed in the fœtal thorax, yet in order, and in readiness for action, the first moment that the occasion requires its service. This is having a machine locked up in store for a future use; which incontestably proves, that the case was expected to occur, in which this use might be experienced: but expectation is the proper act of intelligence. Considering the state in which an animal exists before its birth, I should look for nothing less in its body than a system of lungs. It is like finding a pair of bellows in the bottom of the sea; of no sort of use in the situation in which they are found; formed for an action which was impossible to be exerted; holding no relation or fitness to the element which surrounds them, but both to another element in another place.
As part and parcel of the same plan, ought to be mentioned, in sneaking of the lungs, the provisionary contrivances of the foramen ovale and ductus arteriosus. [Pl. XXIX.] In the fœtus, pipes are laid for the passage of the blood through the lungs; but, until the lungs be inflated by the inspiration of air, that passage is impervious, or in a great degree obstructed. What then is to be done? What would an artist, what would a master do upon the occasion? He would endeavour, most probably, to provide a temporary passage, which might carry on the communication required, until the other was open. Now this is the thing which is actually done in the heart: instead of the circuitous route through the lungs, which the blood afterwards takes before it gets from one auricle of the heart to the other, a portion of the blood passes immediately from the right auricle to the left, through a hole placed in the partition which separates these cavities. This hole anatomists call the foramen ovale. There is likewise another cross cut, answering the same purpose, by what is called the ductus arteriosus, lying between the pulmonary artery and the aorta. But both expedients are so strictly temporary, that after birth the one passage is closed, and the tube which forms the other is shrivelled up into a ligament. If this be not contrivance, what is?
But, forasmuch as the action of the air upon the blood in the lungs appears to be necessary to the perfect concoction of that fluid, i.e. to the life and health of the animal, (otherwise the shortest rout might still be the best,) how comes it to pass that the fœtus lives, and grows, and thrives, without it? The answer is, that the blood of the fœtus is the mother’s; that it has undergone that action in her habit; that one pair of lungs serves for both. When the animals are separated, a new necessity arises; and to meet this necessity as soon as it occurs, an organization is prepared. It is ready for its purpose; it only waits for the atmosphere; it begins to play the moment the air is admitted to it.