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conformation fo happy was not the gift of chance.

In birds this organ affumes a new character; new both in fubftance and in form, but, in both, wonderfully adapted to the wants and ufes of a diftinct mode of existence. We have, no longer, the fleshy lips, the teeth of enamelled bone; but we have, in the place of these two parts, and to perform the office of both, a hard fubftance (of the fame nature with that which composes the nails, claws, and hoofs of quadrupeds) cut out into proper fhapes, and mechanically fuited to the actions which are wanted. The sharp edge and tempered point of the Sparrow's bill, picks almoft every kind of feed from its concealment in the plant; and not only fo, but hulls the grain, breaks and fhatters the coats of the feed, in order to get at the kernel. The booked beak of the hawk tribe, separates the flesh from the bones of the animals which it feeds upon, almost with the cleanness and precision of a diffector's knife. (The butcher bird transfixes its prey upon the fpike of a thorn, whilft it picks its bones.) In fome birds of this class, we have the cross bill, i. c. both the upper and lower bill hooked, and their tips croffing. The poon bill, en

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ables the goose to graze, to collect its food from the bottom of pools, or to seek it amidst the foft or liquid fubftances with which it is mixed. The long tapering bill of the snipe and woodcock, penetrates ftill deeper into moift earth, which is the bed in which the food of that fpecies is lodged. This is exactly the inftrument which the animal wanted. It did not want ftrength in its bill, which was inconfiftent with the flender form of the animal's neck, as well as unneceffary for the kind of aliment upon which it fubfifts; but it wanted length to reach its object.

But the fpecies of bill which belongs to birds that live by fuction, deferves to be defcribed in its particular relation to that office. They are what naturalifts call ferrated or dentated bills; the infide of them, towards the edge, being thickly fet with parallel or concentric rows, of fhort, ftrong, sharp-pointed prickles. These, though they should be called teeth, are not for the purpose of maftication, like the teeth of quadrupeds; nor yet, as in fish, for the feizing and retaining of their prey; but for a quite different use. They form a filter. The duck by means of them difcuffes the mud; examining, with great accuracy,

curacy, the puddle, the brake, every mixture which is likely to contain her food. The operation is thus carried on. The liquid or femiliquid fubftances, in which the animal has plunged her bill, fhe draws, by the action of her lungs, through the narrow interftices which lie between these teeth; catching, as the ftream paffes across her beak, whatever it may happen to bring along with it, that proves agreeable to her choice, and eafily difmiffing all the reft. Now fuppofe the purpose to have been, out of a mass of confufed and heterogeneous fubftances, to separate for the use of the animal, or rather to enable the animal to separate for its own, thofe few particles which suited its tafte and digeftion, what more artificial, or more commodious, inftrument of selection, could have been given to it, than this natural filter? It has been obferved alfo, what must enable the bird to choose and diftinguish with greater acuteness, as well, probably, as what increases its gratification and its luxury, that the bills of this fpecies are furnished with large nerves, that they are covered with a fkin, and that the nerves run down to the very extremity. In the curlew, woodcock, and fnipe, there are three pairs of nerves, equal almost to

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the optic nerve in thickness, which pafs firft along the roof of the mouth, and then along the upper chap down to the point of the bill, long as the bill is.

But to return to the train of our obfervations. The fimilitude between the bills of birds and the mouths of quadrupeds, is exacly fuch, as, for the fake of the argument, might be wifhed for. It is near enough to fhew the continuation of the fame plan: it is remote enough to exclude the fuppofition of the difference being produced by action or ufc. A more prominent contour, or a wider gape, might be refolved into the effect of continued efforts, on the part of the fpecies, to thrust out the mouth, or open it to the ftretch. But by what course of action, or exercise, or endeavour, fhall we get rid of the lips, the gums, the teeth; and acquire, in the place of them, pincers of horn? By what habit shall we fo completely change, not only the shape of the part, but the fubftance of which it is composed? The truth is, if we had feen no other than the mouths of quadrupeds, we fhould have thought no other could have been formed little could we have fuppofed, that all the purposes of a mouth, furnished with

lips, and armed with teeth, could be answered by an inftrument which had none of these; could be fupplied, and that with many additional advantages, by the hardnefs, and sharpnefs, and figure, of the bills of birds.

Every thing about the animal mouth is mechanical. The teeth of fish, have their points turned backwards, like the teeth of a wool- or cotton-card. The teeth of lobsters, work one against another, like the fides of a pair of fhears. In many infects, the mouth is converted into a pump or fucker, fitted at the end fometimes with a wimble, sometimes with a forceps; by which double provision, viz. of the tube and the penetrating form of the point, the infect first bores through the integuments of its prey, and then extracts the juices. And, what is moft extraordinary of all, one fort of mouth, as the occafion requires, fhall be changed into another fort. The caterpillar could not live without teeth; in feveral fpecies, the butterHly formed from it, could not use them. The old teeth therefore are caft off with the exuviæ of the grub; a new and totally different apparatus affumes their place in the fly. Amidst these novelties of form, we fometimes forget that it is, all the while, the animal's mouth; that, whether it be lips, or teeth, or bill,

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