There are many spring waters which are used as beverages and drunk either with or between meals. They possess, in addition to the properties of plain water, a mildly tonic effect upon the mucous membrane of the stomach, due either to the carbon-dioxide gas or salts, or both, which they may contain, and, owing to their salts and water, they are also diuretic. Many of these waters are sold "plain" - i. e., without free gas, and others either hold natural C02 or are made "sparkling " by having this gas pumped into them under pressure.

These waters are very useful, when taken half an hour before meals, to cleanse the mucous membrane of the stomach and prepare it for the reception of food. They also serve to dilute and wash out waste materials from the system.

The effervescing or carbonic-acid waters are more highly charged with gas as sold from " fountains " at the druggists' or in siphons than when bottled.

Fruit sirups are combined in many ways with soda, carbonic-acid, or other effervescing waters, to make soda water and similar beverages.

Ginger ale, sarsaparilla, etc., are made effervescing, and are often used as cooling and refreshing drinks.

The habit which some persons form of drinking large quantities of alkaline waters independent of any special needs of the system should be condemned. It leads to the condition which Trousseau long ago described as "mineral-water cachexia".

All the effervescing waters when taken in excess are apt to excite or increase flatulency and give rise eventually to dyspepsia and debility, especially when combined with sweet sirups. They should be avoided in dilatation of the stomach, flatulent dyspepsia, and palpitation.

Some waters are drunk for their laxative or purgative action, and others for the salts which they contain, like those of sulphur, iron, or arsenic. This leads to the classification of mineral waters into alkaline, saline, chalybeate, sulphurous, acidulous, arsenical, etc.

Thermal waters are those which issue hot from their springs. Many persons believe that these waters possess special properties by virtue of being hot, which they lose as the heat departs, but there is no physiological ground for this belief.

Many table waters, like Poland water (a plain carbonic-acid water), Vichy, Johannis, Apollinaris, and Seltzer (effervescing carbonic-acid waters), are used mainly as an agreeable table beverage, and to dilute spirits, wines, lemonade, etc. They are cooling, refreshing, arid wholesome. People will often drink fluid of this kind who are not willing to drink sufficient plain water.

Johannis water is an alkaline carbonated water which comes from a spring at Zollhaus, in the Taunus Mountains. It contains principally carbonates of lime, soda, and magnesia, besides traces of other materials, and considerable free carbonic-acid gas.

A glass of Apollinaris or similar water taken an hour after a too heavy dinner promotes digestion and helps remove waste products from the system. In fevers such waters are always useful, and they may be given very freely. They often allay nausea and vomiting. They may be employed for the dilution of liquors and milk for invalids. Some persons can digest milk better when diluted with Vichy, carbonic-acid water, plain soda water, or Seltzer. The addition of the latter tends to overcome the constipation which milk is apt to cause.

Some waters are sold as natural lithia waters, but the quantity of lithium contained in any spring water is usually very minute, and beverages of this class are generally re-enforced artificially by lithium salts. They are used to counteract the lithic-acid diathesis, gout, and rheumatism.

Kronenquelle water is an alkaline lithia water from Obersalz-brunn, in Silesia, which contains considerable sodium carbonate and traces of iron and manganese.

The Buffalo, Londonderry (New Hampshire), and other lithia waters are much prescribed in this country.

Below is given a list of some of the more noted waters which are extensively used in conjunction with dietetic treatment: