Thirst the best guide in taking simple drinks--Thirst increased by diminution of the circulating fluids--The desire for liquids generally an indication of their propriety--Much fluid hurtful at meals--Most useful three or four hours later--The temperature of drinks is of consequence--Curious fall of temperature in the stomach from cold water--Ices hurtful after dinner--Useful in warm weather, when digestion is completed and caution used--Cold water more dangerous than ice when the body is overheated--Tepid drinks safest and most refreshing after perspiration--Kinds of drink--Water safe for every constitution--Wine, spirits, and other fermented liquors, too stimulating for general use, but beneficial in certain circumstances--Test of their utility. On the subject of drinks two questions naturally occur. _When_ ought we to drink? and, _What_ ought we to drink? On both I shall offer a few very brief remarks. In the first part of this volume I endeavoured to shew that the sensation of _thirst_ is given to us for the express purpose of impelling us to take liquids whenever the wants of the system require them, and that, in all ordinary circumstances, we cannot have a better or a safer guide. Such is the general case; but exposed as we are to numerous deviations from the intentions of Nature in our ways of living, a few precautionary observations may not be without use. The quantity of fluid separated from the blood and thrown out of the system, in the course of twenty-four hours, by perspiration, exhalation from the lungs, the urinary discharge, and the various other secretions, is very great; and were not the loss as regularly supplied by the ingestion of liquid, either as food or as drink, the blood would speedily become so thick as to be unfit for circulation. This actually happens in spasmodic cholera, in which the serum or watery portion of the blood passes off through the bowels with such rapidity, as to cause the entire suppression of the urinary secretion, and in which consequently, the urgency of thirst is almost always excessive. In the healthy state, however, the loss of fluid is never too rapid unless under severe exertion or exposure to a very high temperature, both being circumstances in which it is well known that thirst becomes urgent in proportion to the necessities of the frame.