The _immediate_ effect of a cold bath is to chill the _surface_ of the body, the temperature of which, as tested by a thermometer, may fall several degrees. At the same time there is produced a pallor of the surface and goose-skin. While the surface is cooled, however, the blood itself undergoes an increase of temperature, due to an increase of the combustion processes going on in the body, of which we get additional evidence in the increase of the rate of the pulse and respiration, and an augmented discharge of carbonic acid from the lungs. There is a sudden sense of chilliness, and this impression, made upon the nerves of the skin, produces, by its action on the brain and spinal cord, some slight mental excitement and shivering of the limbs. After the bath has been continued some little time the temperature of the blood falls (sometimes as much as three or four degrees), the pulse and respiration get slow, the shivering gives place to lassitude, and the mental excitement to listlessness. On removal from the bath the phenomenon of “reaction” sets in. The vessels of the skin enlarge, the chilliness gives place to warmth, and the feeling of uneasiness is succeeded by a sense of comfort. This reaction follows most quickly when the bath is of short duration, and when its effects are suddenly induced. The shorter the bath the less is the ultimate depression of the temperature of the blood. The shorter the bath the greater is its power of _stimulating_ function; the longer it is continued the greater is the effect of _cooling_. The effect of a _warm_ bath is to raise slightly the temperature of the surface and the temperature of the blood. The pulse and respiration are both quickened, and the escape of carbonic acid from the lungs is also increased. The blood-vessels of the skin get dilated, and the surface is reddened in proportion to the heat of the water. Warm baths of a moderate temperature can be borne for a longer time than cold baths; but if the temperature be too high, and the bath too long-continued, faintness is liable to occur. On removal from the hot bath the skin is in a very delicate and susceptible state, and the vessels are liable to “re-act” in the direction of extreme contraction, in which case dangerous internal congestion may occur. If, however, the skin be protected, and the patient be placed in a warm room, or in bed, a violent perspiration will ensue. In the cold bath the muscles are liable to become stiff; but in the warm bath a stiff and fatigued muscle will resume its suppleness. After a hard day’s hunting a warm bath is a well-known and agreeable luxury.