plant, which spreads uncommonly from its numerous seeds, it often becomes a troublesome weed, if it be once suffered to grow in fields. Nevertheless, Dr. Anderson recommends its cuhure as a proper food for cattle.—It is eaten by sheep and hogs; but is relished neither by horses, cows, nor goats.
YAWNING is an involuntary opening of the mouth; which is occasioned by weariness, or an inclination to sleep; though it frequently occurs early in the morning, and immediately after rising.
Yawning is performed by extending all the muscles, that are capable of spontaneous motion; by expanding the lungs; by slowly and gradually inhaling a large portion of air, and expiring or breathing it out, after it has been rarefied in the body; and lastly, by restoring the muscles to their natural position. Persons of strong and healthy constitutions are most liable to this natural impulse, when they awake, on account of the perspirable matter that lodges in the pores of the skin: hence Boerhaave observes, that yawning appears to be designed by Nature, to move, accelerate, and uniformly to distribute the humours throughout the system; consequently, to render the various muscles capable of discharging their respective functions. Such involuntary motion, therefore, greatly conduces to health; but, if it become habitual, or be too often repeated, especially by persons of sedentary lives, it will be advisable to take a short walk in the fresh air, and to inspire a large portion of that salutary fluid, in temperate weather. Sometimes, however, yawning is the fore-runner of convulsions or ague-fits; in which cases, those distressing affections might often be prevented, by adopting timely and proper remedies.
Year. See Kalendar.
YEAST, or Barm, is the froth or scum which rises on beer, during the act of fermentation.
Yeast is an article of the greatest importance in domestic economy; forming a necessary ingredient in bread, which would otherwise become heavy and unwholesome. As it cannot at all times be obtained in sufficient quantities, we propose to state various methods which have been contrived, for generating and preserving this commodity.
In the 2d vol. of the "Memoirs of the Philosophical and Literary Society of Manchester," Mr. Henry has published a method of preparing artificial yeast, by which good bread may be made, without the aid of any other ferment. He directs flour and water to be boiled to the consistence of treacle; and, when the mixture is cold, to saturate it with fixed air. Next, it must be poured into large bottles with narrow mouths, which should be loosely covered with paper; and, over this, with a slate and a weight, to keep them steady. The bottles ought now to be placed in a room, the temperature of which is from 70 to 80°; and the mixture be stirred two or three times in the course of 24 hours. At the end of about two days, according to Mr. H., such a degree of fermentation will have ensued, that the mixture acquires the consistence of yeast. In this state, the flour, intended to be made into bread, must be incorporated with such artificial barm, in the proportion of 6lbs. of the former to one quart of the latter, and a due quantity of warm water. The whole is now to be kneaded together in a
