YAWS. Syn. Frambœsia, L. A peculiar disease of the skin, common in the Antilles and some parts of Africa. It is characterised by mulberry-like excrescences, which discharge a watery humour. The treatment chiefly consists in alleviating urgent symptoms (if any), and the adoption of a temperate diet and regimen, until the eruptions, having run their course, begin to dry, when tonics and alteratives, as cinchona bark, quinine, and sarsaparilla, with occasional small doses of mercurials, generally prove advantageous. The master (or principal) yaw, which frequently remains troublesome after the others have disappeared, may be dressed with the ointment of red oxide of mercury, or of nitrate of mercury, diluted with an equal weight of lard.
The yaws is not a dangerous, although a very disgusting, disease. It is contagious by contact, and, like the smallpox, only occurs once during life.
YEAST. Syn. Barm, Ferment, Zumine; Fermentum, L. Yeast, which consists almost entirely of minute vegetable cells, termed Torula cerevisiæ, is either the froth or the deposit of fermenting worts, according to the character of the fermentation.
The top yeast, or superficial ferment, which covers the surface of fermenting worts, is called ‘oberhefe’ by the Germans; and the bottom yeast, or the ferment of deposit, is termed ‘unterhefe,’ The first is the common yeast of the English brewer; the other, that used in Bavaria for the fermentation of worts from below (untergärung). Both varieties yield their own kind under proper conditions. Wort fermented with top yeast, at from 46° to 50° Fahr., yield both varieties, and each of these furnishes its own kind, nearly pure, by a second fermentation. See Brewing, Fermentation, &c.
Pres. 1. Ordinary beer yeast may be kept fresh and fit for use for several months, by placing it in a close canvas bag, and gently and gradually squeezing out the moisture in a screw press until the remaining matter acquires the consistence of clay or soft cheese, in which state it must be preserved in close vessels, or wrapped in waxed cloth. This is the method generally adopted for the best Flanders and German yeast.
2. Whisk the yeast until it forms a uniform liquid mass, and then lay it with a clean and soft painter’s brush evenly and thinly on flat dishes, or any convenient surface, on which it can be exposed to the sun or air; this operation must be repeated as soon as the first coat is sufficiently solid, and so on, until the layers acquire a proper thickness, when it must be detached and preserved as before. If rendered quite dry, its power of exciting fermentation will be destroyed.
3. By employing strips of clean new flannel (well washed), as above, and, when sufficiently dry, rolling these up, and covering them with waxed cloth or paper, or placing them in tin canisters or boxes. For use, a few inches of one of the strips is cut off, and soaked in lukewarm water, when the barm leaves the flannel, and mixes with the water, which may then be stirred up with the flour.
Yeast, Artifi′′cial. “Although the conversion of a small into a large quantity of yeast is a very easy thing, yet to produce that substance from the beginning is very difficult.” (Berzelius.) Both cases are met in the formulæ below.
Prep. 1. (Without a ferment.)—a. (Fownes.) Wheat flour is to be mixed with water into a thick paste, which is to be slightly covered, in a moderately warm place; about the third day it begins to emit a little gas, and to exhale a disagreeable sour odour; about the sixth or seventh day the smell changes, much gas is evolved, accompanied by a distinct and agreeable vinous odour, and it is then in a state to excite either to vinous or panary fermentation, and may be either at once employed for that purpose or formed into small and very thin cakes, dried in the air and preserved for future use. Wort fermented with it in the ordinary way yields a large quantity of yeast, of excellent quality, which is found at the bottom of the vessel. “This is a revival of a method which, although Mr Fownes seems to regard it as new, is to be found in the ‘Chemistry’ of Boerhaave” (‘Lancet.’) It is, indeed, a mere modification of the mode of preparing leaven, as practised from the most remote ages of antiquity; but is not the less valuable on that account.
2. (With a ferment.)—a. Take of bean flour, 1⁄4 lb.; water, 6 quarts; boil for 1⁄2 an hour, pour the decoction into any suitable vessel, add of wheat flour, 31⁄2 lbs.; stir the whole well together, and, when the temperature reaches 55° Fahr., add of beer yeast, 2 quarts; mix well, and in 24 hours after the commencement of the fermentation add of barley or bean flour, 7 lbs.; make a uniform dough by thorough kneading, form it into small cakes, as above, and then preserve these in a dry situation. For use, one of these discs is to be broken into pieces, laid in tepid water, and set in a warm place during 12 hours, when the soft mass will serve the purpose of beer yeast.