We have already carefully considered the important part played by water in metabolism, and have indicated the necessity of a sufficient supply thereof to subserve the nutritional functions of the economy. We are sufficiently familiar with the "water cure" to know in a general way that the annual pilgrimage which so many patients undertake to a home or foreign spa is mainly for the purpose of "washing" something out of their tissues. That the physicians of the early part of the eighteenth-century were already well acquainted with some similar process is evident from the vegetarian Dr. Sangrado's advice to Gil Bias, who was inclined to plead ignorance of therapeutics. "You need not waste your time in studying the nonsense written by other doctors. You have only to follow my method. Never give a patient medicine. Bleed him well, and tell him to drink a pint of hot water every half-hour. If that does not cure him, well - it's time he died."

Whatever other treatment be adopted, and whatever other factors may be in operation, it is usually held to be essential to consume a sufficient amount of water during the "cure," although in some spas this quantity is by no means distinguished by its magnitude. As there is usually - though not always - some ingredient in solution in the water, there is an inclination to attribute the beneficial influence derived from residence at a spa to this substance, although its amount may be so insignificant that chemists have great difficulty in isolating it, and even sceptical local doctors are inclined to ascribe the effect to some occult dynamism resident in the water itself. I have little hesitation in saying that quite an appreciable portion of the benefit derived from spa treatment must be assigned to the influence of pure water employed both externally and internally in unaccustomed quantity and manner.