may be momentarily assuaged by wetting the mouth, or holding a thin fluid in it — yet it can only be effectually relieved by conveying into the stomach a quantity of fluid sufficient to supply the deficiency. This supply is termed dilution, from the fact that the fluid is absorbed and carried into the blood, which it renders thin, and the fluids themselves are called diluents. Thirst, however, does not always indicate a deficiency of fluids in the circu- lating mass, and the tongue and fauces are occasionally dry and harsh whilst the sensation of thirst is absent. Some individuals never experience the sensa- tion of thirst. Mr. Alcott, who lives entirely on succulent vegetables, states that he has drunk no fluids for more than a year past, and that he never experiences the sensation of thirst — a similar case is mentioned by Sauvages, of an indivi- dual who never thirsted, and passed whole months of the hottest weather with- out drinking. It is well known that many warm-blooded animals such as mice, quails, parrots, rabbits, &c, drink but very little ; which is supposed to be owing to the circumstance that they have very large salivary glands, and a larger pancreas in proportion to the size of their bodies. In general, as we have already remarked, thirst is indicative of diminished fluidity of the blood and when it is not assuaged by taking liquids into the stomach, or by moistening the mouth with them, or by apply- ing them to the surface, the torment which it induces amounts occasionally almost to phrenzy, and is borne with less patience and greater difficulty than hunger; some- times inflammation of the mouth and throat and intense fever supervene. Various circumstances connected with the ordinary condition of the body influence the sen- sation of thirst. Thus it is greater in infancy and childhood than in adult age, and less in old age ; it is greater in women than in men ; it is varied by constitution and temperament ; by climate ; season ; the nature of the diet ; exercise ; passions of mind, and even by imagination. As an aliment, water is of prime necessity to all organized beings. As a solvent, it reduces to a fluid mass all the principles neces- sary for the growth of animal and vegetable bodies ; which must be in a fluid form, 149 before they can be taken up by the fine lacteal and other absorbent vessels, and thug carried to every part of the living tissue. How important then, that this universal solvent should be pure, — that it should be free from those foreign ingredients, whe- ther of animal, vegetable or mineral origin, which, if introduced into the system, tend to disturb the functions of the various organs, and often to occasion serious derangement and disease. But besides its important office as a menstruum, water is perhaps the most important nutrient, of all those which sustain the existence of organized bodies. A great proportion of that which is drunk, is speedily absorbed by the veins, and carried into the circulation, some time before the product of the digested food is introduced by the way of the laeteals. There are numerous cases on record, where persons have lived, for a considerable length of time, on water alone. In the " Transactions of the Albany Institute," for 1830, Dr. M'Naughten relates the case of a man who was sustained on water alone, for 53 days. " For the first six weeks he walked out every day, and sometimes spent a great part of the day in the woods. His walk was steady and firm, and his friends even remarked that his step had an unusual elasticity; he shaved himself until about a week before his death, and was able to sit up in bed till the last day." To the evils which result from the use of impure water, we have already alluded, although it would require far more space than has been assigned to us in this Appendix, to do them adequate justice. There can be no doubt, that the chief cause of the excess of mortality in cities, over that of the country, is to be found in the impure water, with which the former are so generally supplied, and we may confidently predict, that in consequence mainly of the introduction of the Croton River into the City of New-York, no city in the world of equal size, will surpass it in salubrity. To the operation of the same cause, we may doubtless look with confidence for a decided improvement in personal comeliness and beauty. " It is evident," says Dr Jackson, " that the health of a whole community may be so affected by impurities in water drank by