This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
The sense of weakness and exhaustion referred especially to the lower part of the spine, occurring in delicate subjects after overexertion of any kind, and due probably to a passive congestion, is much relieved by cold "spinal washings," or gentle douching each day for a short time, and followed by good friction. Dr. Moxon has recently drawn attention to the comparatively feeble circulation in the lower part of the cord, and doubtless such remedies act by quickening and regulating the blood-current in that part (Croonian Lectures, British Medical Journal, i., 1881).
The more acute backache, commonly felt by women, and in the absence of definite cause traceable often to "anaemia of the cord" (Bartholow), is better relieved by hot applications; and if the douche be not obtainable, then a hot sponge or fomentation will serve.
Preissnitz and his early followers combined with the outward application of cold water its immoderate and excessive use internally, an error which led to some evil result, and which is not often now repeated. Water-drinking is now ordered on general dietetic principles rather than as an essential part of a hydropathic course (Braun, chap. v.). In chronic illness good results are more rapidly and easily obtained by the use of mineral waters in moderate quantities, and containing salts and gas, so that the number of illnesses in which ordinary water is internally employed as a remedy is not large. Its most common internal use, medicinally, is as a solvent and diluent.
In Fevers of all kinds it is used to lessen thirst, to lower temperature, and restore the balance of fluid constituents of the tissues; also to promote secretion and the elimination of waste products.