sequence of the alkaline tartrate being converted into an alkaline carbonate (see pp. 28 and 29), which passes out of the system in the urine, and promotes the deposition of the earthy phosphates.

Acidulated Drops or Lozenges, consist of barleysugar sharpened with tartaric acid, as I have before stated (see pp. 118, 119). They are useful in coughs and sore-throats, but are commonly taken, on account of their agreeable flavour, as articles of confectionary.

4. Malic Acid, or Acid of Apples. - This acid is very extensively distributed in the vegetable kingdom. It exists in the free state in Apples, Pears, Quinces, Plums, Apricots, Peaches, Cherries, Gooseberries, Currants, Strawberries, Raspberries, Blackberries, Pineapples, Barberries, Elderberries, Grapes, Love-apples, Tamarinds, and several other fruits. It is usually accompanied by citric acid. Wine, Cider, and Perry, likewise contain it. The formula for the hydrated acid is C H O3 + Aqua2. Its dietetical properties are analogous to citric acid; but it is not employed in the separate state.

5. Oxalic Acid.-This exists in a considerable number of plants. Those which it is necessary here to refer to, as being employed at the table, are the Garden Rhubarb, whose leafstalks are used in tarts and puddings; Common Sorrel, which is sometimes taken as a potherb and salad; and Common Woodsorrel, which is occasionally eaten as an antiscorbutic. The crystallised acid of the shops is obtained by the action of nitric acid on sugar, or molasses. Its formula is C2 O3 + Aqua3. In large doses and in a concentrated form, it is an energetic poison; but in small quantities and largely diluted, it may be used without injury.

In this country it is never taken internally. In France, however, it is sometimes employed in the preparation of acidulous drinks (called lemonades), in the proportion of twelve or fifteen grains of acid to a quart of water; but it is much safer to use tartaric acid. Lozenges containing this acid have been prepared under the name of Tablettes d'Acide Oxalique, or Pastilles pour la soif; but they present no advantage over the ordinary acidulated drops.

Quadroxalate of Potash, sold in the shops as Salt of Sorrel, has also been employed in the preparation of refrigerant drinks and lozenges.

6. Lactic Acid, or Milk Acid. This acid exists in sour milk. It is also formed when various vegetable substances become sour-as when oatmeal is left in a large quantity of water. Its composition and formation out of sugar have been already adverted to (see p. 115). "This acid," says Dr. Prout, "like the acetic acid, is probably, under certain circumstances, capable of becoming an aliment; but as it is often found unchanged and even developed in the stomach, and, indeed, in almost all parts of the animal system, it is probably less digestible, and, therefore, less adapted as an aliment, than the acetic acid." Under the erroneous idea that lactic acid was one of the agents by which aliments are dissolved in the stomach, lactic acid lemonade, and lactic acid lozenges, have been employed in dyspepsia arising from simple debility of the digestive

organs.

7. Tannic Acid..-This, though a constituent of some articles employed at the table, as Tea, can scarcely be considered alimentary.

8. THE ALCOHOLIC ALIMENTARY PRINCIPLE.

The reasons for believing that under some circumstances alcohol is an alimentary principle, have been already stated (See pp. 50, 51, 52, and 54).

The formula for pure or anhydrous alcohol (sp. gr. 0-7947 at 60° F.) is C H O2. Spirit of Wine consists of alcohol and water. Rectified spirit of wine (sp. gr. 0.835 to 840) contains about 90 per cent. of alcohol.

Alcohol is a product of the vinous fermentation. It is, therefore, a constituent of Wines, Cyder, Perry, and Malt liquors (Beer, Ale, and Porter), and of Ardent Spirits obtained by distillation from vinous liquids. The following are the quantities of alcohol contained in various Wines, Spirits, and Malt Liquors, according to the best authorities.

TABLE of the proportion of ALCOHOL (sp. gr. 0.825, at 6o F.), by measure, contained in 100 parts of Wine, Spirits, Malt Liquors, &c.

* A. means average, F. Julia-Fontenelle, P. Prout.

According to the more recent experiments of Dr. Christison, the quantity of alcohol in wines has been somewhat overrated. The following are his results :

Dr. Christison states that by keeping wines, as Sherry and Madeira, in casks, for a moderate term of years, the quantity of alcohol increases; but after a certain time it decreases; and it is probable that at the period when wines begin to lose alcohol they cease to improve in flavour.

The value of ardent spirits is, of course, proportionate to the quantity of alcohol contained therein; and, therefore, a ready mode of estimating this is most desirable. The alcoholometrical method usually adopted consists in determining the sp. gr. of the