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

But, forafmuch as the action of the air 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, (otherwife the shortest rout might ftill be the best, 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 pair of lungs ferves for both.

habit; that one

When the animals are separated, 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 inftruments; the fitnefs of fuck. 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 obferved 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 inftance, the feveral parts of a watch, the spring, the barrel, the chain, the fusee, the balance, the wheels of various fizes, forms, and pofitions, what is it which would take the obferver's attention, as most plainly evincing a conftruction, directed by thought, deliberation, and contrivance? It is the suitableness of these parts to one another, firft, in the fucceffion and order in which they act; and, fecondly, with a view

to

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 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 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 reft of the works, he faw, when he came to underftand its action, that which rendered their motions equabie. Laftly, in looking upon the index and face of the watch, he saw the use and conclufion of the mechanism, viz. marking the fucceffion of minutes and hours; but all depending upon the motions within, all

upon

upon the system of intermediate actions between the spring and the pointer. What thus ftruck his attention in the feveral parts of the watch he might probably defignate by one general name of "relation:" and obferving, with respect to all the cafes whatever, in which the origin and formation of a thing could be afcertained by evidence, that these relations were found in things produced by art and defign, and in no other things, he would rightly deem of them as characteristic of fuch productions. To apply the reasoning here defcribed to the works of nature.

The animal œconomy is full; is made up of these relations.

I. There are firft, what, in one form or other, belong to all animals, the parts and powers which fucceffively act upon their food. Compare this action with the process of a manufactory. In man and quadrupeds, the aliment is, first, broken and bruised by mechanical inftruments of maftication, viz. fharp spikes or hard knobs, preffing against, or rubbing upon, one another: thus ground and comminuted, it is carried by a pipe into the ftomach, where it waits to undergo a great chymical action, which we call digestion:

when

when digested, it is delivered through an orifice, which opens and fhuts as there is occafion, into the first inteftine: there, after being mixed with certain proper ingredie:s, poured through a hole in the fide of the veffel, it is further diffolved: in this ftate, the milk, chyle, or part which is wanted, and which is fuited for animal nourishment, is ftrained off by the mouths of very small tubes, opening into the cavity of the inteftines: thus freed from its groffer parts, the percolated fluid is carried by a long, winding, but traceable course, into the main ftream of the old circulation; which conveys it, in its progrefs, to every part of the body. Now I fay again, compare this with the procefs of a manufactory; with the making of cyder, for example, the bruising of the apples in the mill, the fqueezing of them when fo bruised in the press, the fermentation in the vat, the bestowing of the liquor thus fermented in the hogsheads, the drawing off into bottles, the pouring out for use into the glass. Let any one shew me any difference between these two cafes, as to the point of contrivance. That which is at prefent under our confideration, the "relation"

of