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portionably stronger, as the machinery is more complicated, and the adaptation, more exact.
IV. What has been faid 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 exclusion 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 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 fame plan, ought to be mentioned, in speaking of the lungs, the provifionary contrivances of the foramen ovale and ductus arteriofus. 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 pasfage is impervious, or in a great degree obstructed. What then is to be done 2 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 get 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 fame purpose, by what is called the duftus arteriofus, lying between the pulmonary artery and the aorta. But both expedients are
so so strictly temporary, that, after birth, the one paflage is closed, and the tube which forms the other shrivelled up into a ligament. If this be not contrivance, what is?CHAPTER XV.
But, forasmuch as the action of the ir upon the blood in the lungs, appears to be necessary to the persect concoction of that fluid, i. e. to the life and health of the animal, (otherwise the shortest roiremij,ht 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 fetus 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 neceflity 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.
En several different parts contribute to one effect; or, which is the fame thing, when an effect is produced by the joint action of different instruments; the witness of such parts or instruments to one another, for the purpose of producing, by their united action, the effect, is what I call relation: and whereever this is observed in the works of nature or of man, it appears to me to carry along with it decisive evidence of understanding, intention, art. In examining, for instance, the several parts of a watch, the spring, the barrel, the chain, the fusee, the balance, the wheels of various sizes, forms, and positions, what is it which would take the observer's attention, as most plainly evincing a construction, directed by thought, deliberation, and contrivance? It is the suitableness of these parts to one another, first, in the succession and order in which they act; and, secondly, with a view
to the effect finally produced. Thus, referring the spring to the wheels, he sees, in it, that which originates and upholds their motion; in the chain, that which transmits the motion to the fusee ; In the fusee, that which communicates it to the wheels; in the conical figure of the fusee, if he refer back again to the spring, he sees that which corrects the inequality of its force. Referring the wheels to one another, he notices, first, their teeth, which would have been without use or meaning, if there had been only one wheel, or if the wheels had had no connection between themselves, or common bearing upon some joint effect; secondly, the correspondency of their position, so that the teeth of one wheel catch into the teeth of another; thirdly, the proportion observed in the number of teeth of each wheel, which determines the rate of going. Referring the balance to the rest of the works, he faw, when he came to understand its action, that which rendered their motions equable. Lastly, in looking upnn the index and face of the watch, he faw the use and conclusion of the mechanism, viz. marking the succession of minutes and hours; but all depending upon the motions within, all