5. Removal of Obstructions.—A very large class of diseases are attributable to obstruction in various organs, caused by the reception of foreign matters into the system, and the accumulation of the natural waste of the tissues. The warm bath, to remove, external obstructions, and the internal use of water as a solvent for internal sources of obstruction, are the remedies which will achieve success in nearly all cases. Offending substances in the stomach are readily removed by the water emetic; and hardened accumulations in the large intestine are removed with equal facility by means of the enema.

6. Dilution of the Blood.—In fevers, cholera, and other diseases, the blood often becomes abnormally thickened, dark, and viscid, circulating with difficulty, and not imparting due nourishment to the tissues. Nothing but water can remedy this difficulty. It may be got into the blood by absorption from the skin, if the mucous membrane of the stomach will not absorb it.

7. Influence on the Nervous System.—Finally, it is often important to affect certain organs through their nervous centers. Water, properly applied, will accomplish this also. A fomentation applied to the abdomen will often remove headache, and is an excellent remedy for general nervousness, seeming to affect the whole system, just as does galvanic electricity when applied to the same locality, doubtless through the large nervous ganglia located in that region.

Some physicians claim to have obtained peculiar results by the application of heat or cold to the spine. It is said, for example, that cold applied to any portion of the spine will produce an increased circulation in the portion of the body supplied with organic nerves from the part. Hot applications to the spine are said to produce a contrary effect upon corresponding organs. Perhaps there should be still further observations upon this subject before any attempt is made to establish a definite law. It is well known that applications of ice to the spine is an excellent remedy for chorea, and several other nervous diseases.

For general nervous irritability, or nervousness, the warm full bath may be applied with uniform success. Neither hot nor cold applications are generally useful in such cases.

Temperature of Baths.—The thermometer is the only accurate measure of temperature; hence the importance of its use in the administration of baths. Yet the thermometer may be abused. A given temperature may seem warm to one individual and tepid or cool to another. The same difference of sensation will occur in the same individual on different occasions. What seems cool to-day will be thought warm to-morrow. The susceptibility of the body to sensations of heat and cold largely depends upon its condition and the temperature of surrounding objects. In consequence of this physiological fact, it is improper to attempt, as some have done, to fix certain exact temperatures at which baths must be given to all persons under all conditions.

For convenience and perspicuity, the temperatures of baths have been divided into six grades, as given in the following table by Forbes; all who attempt to use the bath according to the directions should carefully learn and preserve the distinctions here made:—

1. Cold Bath,33°to60°F.
2. Cool,60°„75°
3. Temperate,75°„85°
4. Tepid,85°„92°
5. Warm,92°„98°
6. Hot,98°„112°

The vapor bath ranges from 98° to 120°; the hot-air or Turkish bath from 100° to 160°, or even higher, though not usefully so.

A bath of any temperature above the natural heat of the body, 98°, is a hot bath. At 32°, water becomes ice; a bath is very rarely given at this temperature, and then the application should be made to only a small surface. Water at 32°, and even ice and snow, may be usefully employed as topical remedies in local diseases. It will rarely be necessary to employ a full bath at a lower temperature than 65°, which will usually seem very cold to the patient. A temperature from 85° to 95° is the most generally useful for baths which involve a considerable portion of the body, though of course higher temperatures are employed in local applications.