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.
Temperature from 40° to 60° F., according to the season. What is said under "sea-bathing" (v. pp. 151, 152) applies almost equally to the ordinary cold bath taken with a plunge. There is a sudden feeling of chilliness with roughening of the skin (goose-flesh), some blueness of lips, catching of breath, and lowering of pulse. But in a few moments, in fairly healthy persons (and only such should take this form of bath), "reaction" sets in, with sense of warmth and exhilaration, quickening of pulse and respiration, and augmented muscular power. The first effect is due in part to altered conditions of circulation (the superficial vessels being for the moment emptied, and the internal vessels congested), and in part to the sudden shock felt by the large peripheral expanse of sensitive nerve-tissue in the skin. That the nerve-centres can transfer and transmute the sensations and effect of cold, as well as other sensations, might be taken for granted, but a familiar illustration of the fact is presented when one hand only is immersed in cold water, and the sensation is transmitted to the cord and brain, and thence reflected to corresponding nerve-connections on the opposite side, so that the temperature of this opposite limb is also lowered. That the blood-supply of internal organs may be controlled by external applications is proved, inter alia, by the observed contraction of renal arterioles when ice is applied to the lumbar region (Brown-Sequard), and by the immediate diminution of the volume of a congested liver and spleen under the influence of cold douching (Fleury).
The general effect of a short and satisfactory cold bath is "tonic." The blood circulates more freely, and tissue-change is increased; yet, concurrently, appetite and digestive power are so far improved that during a course of such baths weight is commonly gained.
The too-prolonged cold bath, used only through imprudence by the healthy, or for definite curative results in the hyperpyrexial patient, has a very different effect. The primary reaction is succeeded by coldness, depression, weakened circulation, and an exhaustion which may progress to collapse. The temperature is steadily lowered, the blood accumulates in the great venous trunks, capillary circulation and tissue-change generally are interfered with, and reflex symptoms, such as nausea, vomiting, and syncope, may follow. Pugibert and Bailey have lately described a scarlatiniform flush, limited or diffused, as occurring from the cold bath. According to two cases reported by them, this rash is the precursor of shivering, lividity, and a syncope which might prove fatal if it occurred in deep water (Medical Record, August 15, 1879). In the clinical use of the cold bath such results are avoided by careful watching and thermo-metric observation.
Intense cold is an anaesthetic; a mixture of ice and salt applied to the skin for a few moments causes it to assume a white or leaden hue, and in this state incisions can be made into it quite painlessly; the rapid evaporation of ether thrown on to the part in fine spray is also used to produce the same effect.