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 equally employed in hatching and in feeding the young; but this particular mode of nourishment, by means of a substance secreted in their own bodies, is peculiar to certain kinds, and is carried in the crop.

"Besides the Dove kind, I have some reason to suppose parrots to be endowed with the same faculty, as they have the power of throwing up the contents of the crop, and feeding one another. I have seen the cock parroquet regularly feed the hen, by first filling his own crop, and then supplying her from his beak. Parrots, Macaws, Cockatoos, &c., when they are very fond of the person who feeds them, may likewise be observed to have the action of throwing up the food, and often do it. The cock pigeon, when he caresses the hen, performs the same kind of action as when he feeds his young; but I do not know if at this time he throws up anything from the crop.

"During incubation, the coats of the crop in the pigeon are gradually enlarged and thickened, like what happens to the udder of females of class Mammalia in the term of gestation. On comparing the state of the crop, when the bird is not sitting, with its appearance during incubation, the difference is very remarkable. In the first case, it is thin and membraneous; but by the time the young are about to be hatched, the whole, except what lies on the trachea, becomes thicker, and takes on a glandular appearance, having its internal surface very irreeglar. It is likewise evidently more vascular than in its former state, that it may convey a quantity of blood sufficient for the secretion of the substance which is to nourish the young for some days after they are hatched.

"Whatever may be the consistence of this substance when just secreted, it must probably very soon coagulate into a granular white curd, for in such form have always found it in the crop; and if an old pigeon is killed just as the young ones are hatching, the crop will be found as described, and in its cavity pieces of white curd mixed with some of the common food of the pigeon, such as barley, beans, &c.

"If we allow certain of the parents to feed the brood, the crop of the young pigeons, when examined, will be discovered to contain the same kind of curdled substance as that of the old ones, which passes from them into the stomach, where it is digested.

"The young pigeon is fed for a little time with this substance only, as about the third day some of the common food is found mingled with it; as the pigeon grows older the proportion of common food is increased; so that it is seven, eight, or nine days old, before the sceretion of the curd ceases in the old ones, and of course no more will be found in the crop of the young ones.

"I have called this substance curd, not being literally so, but resembling that more than anything I know; it may, however, have a greater resemblance to curd than we are perhaps aware of, for neither this sceretion, nor curd from which whey has been pressed, seems to contain any sugar, and does not run into the acetous fermentation. The property of coagulating is confined to the substance itself, as it produced no such effect when mixed with milk.

"This secretion in the pigeon, like all other animal substances, becomes putrid