The addition of stimulating substances, such as salt, to the water, increases the stimulation to the skin, and the amount of after-reaction.

In sea-bathing the stimulating effect of the salt is further increased by the mechanical shock of the waves, and sometimes also by the friction of the fine sand of the beach. Sea-bathing also differs from baths in the fact that muscular exertion is combined with it, either in simply moving about and retaining one's footing, or still more in swimming.

Carbonic Acid Bath. - This is a saline bath, containing two to three per cent. of chloride of sodium, and not more than one per cent. of chloride of calcium, with varying proportions of free carbonic acid up to 3 grammes in the litre. It has been recommended for chronic heart-disease, both functional and organic, and is said to act as a cardiac tonic.1

Acid Bath. - This bath is made by mixing eight ounces of nitro-hydrochloric acid with a gallon of water at blood heat (98° F.) This is sometimes used as a foot-bath, but it is better applied as a compress. A flannel roller about a foot wide, and long enough to go twice round the body, should be soaked in the acidulated water, wrung thoroughly out, and rolled round the region of the liver; a piece of oil-silk, large enough to cover it completely and leave a little margin over, should then be put over it. It may be worn for several days, being renewed every night, and it is chiefly useful in chronic disease of the liver.1

1 Aug. Schott, Berl. klin. Wochensch., No. 33, 1885.

Alkaline Bath. - This is made by adding crystallised carbonate of sodium to water in the proportion of about one drachm to each gallon. It is chiefly used in chronic skin-diseases.

Sulphurated Bath. - This may be made by dissolving sulphurated potash in water, about half a drachm to the gallon, or, in imitation of Barege waters, may be made by mixing sodium sulphide, sodium carbonate, and sodium chloride in the proportion of twenty grains of each to the gallon. These are chiefly useful in chronic scaly skin-diseases, and in rheumatism. Much more benefit is usually obtained by a visit to sulphur springs, such as those of Aix-les-Bains, Aix-la-Chapelle, Barege, Harrogate, or Strathpeffer, than from the use of sulphur baths at home.

Mustard Bath. - This is made by adding mustard to water in the proportion of about half a drachm to a drachm and a quarter per gallon. It is a powerful stimulant, but must not be applied too long. It must be remembered that, while slight stimuli to the skin increase the frequency and energy of the cardiac contractions and the rapidity of the circulation, and raise the temperature, severe irritation of the skin lessens the frequency of the pulse and the rapidity of the circulation, dilates the vessels and lowers the temperature.2 The patient should never be allowed to remain more than ten minutes in the bath, and should be at once removed as soon as he feels either burning of the skin or icy coldness. Mustard baths are generally used in order to quicken the appearance of the eruption in the exanthemata.

Pine Bath. - This is made by adding a decoction of the shoots of pines to water, but it is more convenient to use the oleum pini sylvestris in the proportion of one minim to the gallon. These baths are used in rheumatism, gout, paralysis, scrofula, and skin-diseases.