This section is from the book "Materia Medica Pharmacy, Pharmacology And Therapeutics", by W. Hale White. Also available from Amazon: Materia Medica Pharmacy, Pharmacology And Therapeutics..
An indifferent bath (88° - 98° F.) 31.1° - 36.6° C, or one in which the bather feels neither hot nor cold, produces no particular effect.
Cold baths increase the production of heat, and abstract heat from the body if they are prolonged; therefore, at first the bodily temperature may rise slightly, but when the loss exceeds the production it falls. The amount of carbon dioxide expired is increased. The rate of the pulse and respiration at first rise, but they soon fall. The skin becomes pale, and the condition of goose-skin is seen. After the bath (the duration and temperature suitable for different persons vary widely) there is a feeling of warmth and exhilaration, and the cutaneous vessels dilate, reaction.
A warm bath, if sufficiently prolonged, may cause a slight rise of the bodily temperature, the skin becomes red, the pulse and respiration are more frequent, the amount of urine secreted is diminished, and after the bath there is profuse perspiration.
Warm water gives rise to nausea and vomiting; hot water, taken in small quantities at frequent intervals, may check both. Water is quickly absorbed from the stomach, and very soon afterwards the amount of urine secreted is greatly increased, and to a less degree the amount of bile, pancreatic juice, and saliva. Large quantities of fluid should not be drunk during meal times, as that impairs digestion. If a considerable amount of water is drunk daily, the amount of urea excreted is increased, and that of uric acid is diminished. Water not only washes out the tissues, but apparently renders tissue metamorphosis more complete.