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portionably ftronger, 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 veffels, where there is no air; elaborately conftructed for the alternate admiffion and exclusion of an elaftic fluid, where no fuch fluid exifts; 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 firft moment that the occafion requires its fervice. This is having a machine locked up in ftore for future ufe; which incontestably proves, that the cafe was expected to occur, in which this use might be experienced: but expectation is the proper act of intelligence. Confidering the state in which an animal exifts before its birth, I should look for nothing lefs in its body than a fyftem of lungs. It is like finding a pair of bellows in the bottom of the fea; of no fort of use in the fituation in which they are found; formed for an action which was impoffible to be exerted; holding no relation or fitness to the element which furrounds them, but both to another element in another place.

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As part and parcel of the fame plan, ought to be mentioned, in fpeaking of the lungs, the provisionary.contrivances of the foramen. ovale and ductus arteriofus. In the fœtus, pipes are laid for the paffage of the blood through the lungs; but, until the lungs be inflated by the infpiration of air, that paffage is impervious, or in a great degree obftructed. What then is to be done? What would an artift, what would a master, do upon the occafion? He would endeavour, moft probably, to provide a temporary paffage, which might carry on the communication required, until the other was open. Now this is the thing, which is, actually, done in the heart. Inftead 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 paffes immediately from the right auricle to the left, through a hole, placed in the partition, which separates thefe cavities. This hole anatomists call the foramen ovale. There is likewife another crofs cut, answering the fame purpose, by what is called the ductus arteriofus, lying between the pulmonary artery and the aorta. But both expedients are

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fo ftrictly temporary, that, after birth, the one paffage is clofed, and the tube which forms the other fhrivelled up into a ligament. If this be not contrivance, what is?

But, forafinuch as the action of the ir upon the blood in the lungs, appears to be neceffary to the perfect concoction of that fluid, i. e. to the life and health of the animal, (otherwise the fhorteft roure might still be the beft,) how comes it to pass that the foetus lives, and grows, and thrives, without it? The answer is, that the blood of the foetus is the mother's; that it has undergone that action in her habit; that one pair of lungs ferves for both. When the animals are feparated, a new neceffity arises; and to meet this neceffity as foon 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.

CHAP

CHAPTER XV.

RELATIONS.

WHEN feveral 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 fitness of such parts or inftruments to one another, for the purpofe 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 decifive evidence of understanding, intention, art. In examining, for instance, the several parts of a watch, the fpring, the barrel, the chain, the fufee, the balance, the wheels of various fizes, forms, and pofitions, what is it which would take the obferver's attention, as moft plainly evincing a conftruction, directed by thought, deliberation, and contrivance? It is the fuitableness of these parts to one another, firft, in the fucceffion and order in which they act; and, fecondly, with a view

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to the effect finally produced. Thus, referring the fpring to the wheels, he fees, in it, that which originates and upholds their motion; in the chain, that which tranfmits the motion to the fufee; 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 fees that which corrects the inequality of its force. Referring the wheels to one another, he notices, firft, their teeth, which would have been without ufe or meaning, if there had been only one wheel, or if the wheels had had no connection between themselves, or common bearing upon fome joint effect; fecondly, the correfpondency of their position, so that the teeth of one wheel catch into the teeth of another; thirdly, the proportion obferved 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. Laftly, in looking upon the index and face of the watch, he saw the use and conclufion of the mechanifm, viz. marking the fucceffion of minutes and hours; but all depending upon the motions within, all

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