II pathologic states, when the stomach will not retain water and when frequent, copious intestinal movements prevent its retention in the blood in quantities that make it diuretic, water can be advantageously administered hypodermically. This method is called hypodermoclysis. A pint or half-pint of sterile, "physiologic" salt solution (i.e., 0.5 to 1 per cent, of sodium chlorid) can be introduced beneath the skin and will be rapidly absorbed and as rapidly eliminated. This is one of the most powerful diuretic measures that can be adopted. Water is also often given by the rectum when it cannot be taken by the stomach. A half-pint or pint of salt solution will be absorbed from the lower intestine. If the latter is irritable, small quantities only should be introduced into it. Unless the rectum be first emptied of its fecal contents, such enemata are of but little use, as they will not long be retained. In many cases, especially of bed-ridden patients, it is well to give a "high" or "colon enema" of salt solution by means of a tolerably thick soft-rubber colon tube, of as large caliber as can conveniently be used. Such tubes are less likely than smaller ones to kink or become bent back upon themselves when pushed through the rectum.

Water or salt solution can be introduced also into the rectum drop by drop continuously. It is then very perfectly absorbed and its presence does not provoke expulsion. The water should be kept at a temperature of 98 to 100° F. in a vessel about 18 inches above the patient. The rectal tube attached to it must have in it a stopcock so adjusted that it will deliver a drop in the rectum about once a second. This is the best method of administering large quantities of fluid constantly to those who need them.

It is often said that to drink water copiously is fattening. Water does not contribute to the production of fat, but it does produce more rapid and better distribution of nourishment throughout the body than occurs when food is eaten and but little fluid is imbibed. To lessen fat-production it is best to diminish the quantity of food eaten and to modify, if need be, its character, but it is best not to lessen unduly or for many days the quantity of water consumed, because that will diminish the elimination of waste, salivary, gastric, and other secretions, and tend to promote constipation and other pathologic states.

Through the agency of drinking-water many harmful impurities are introduced into the body. These may be inorganic chemicals, such as lime, magnesia, iron, and other salts, or micro-organisms. Typhoid fever and cholera are chiefly disseminated by drinking-water. Therefore it is of the greatest importance that the water-supply of a community be free from organized and organic impurities. The inorganic ones do serious harm least frequently, but an excess of lime-salts may increase the tendency of certain individuals to develop renal calculi; and sulphates in abundance may produce annoying purgation.

It is not only necessary that drinking-water shall be pure, but all that is used for cooking purposes and for washing dishes in which food is stored or cooked must also be pure. Not infrequently epidemics of typhoid fever have been traced to milk contaminated by water that contained typhoid bacilli, and that had been used to cleanse the cans in which the milk was stored.

Water is best purified by distillation. Both organic and inorganic impurities can thus be removed. Micro-organisms can be killed by prolonged boiling. When water is boiled, the air is driven out of it and the organic matter in it is often partly decomposed which therefore makes is for the time being at least offensive. This odor is lost by prolonged boiling, for during the process the volatile impurities are driven off. Both distilled and boiled water has a flat, insipid taste, because the air has been expelled from it. It can be made palatable by forcing a current of pure air through it, or by pouring it from pitcher to pitcher or shaking it in a large bottle. In these ways water can be once more aerated.

Filters will remove gross impurities from water. The best will eliminate even most of the micro-organisms. In the course of time, however, the filtering material becomes saturated with bacteria, which are finally washed through in very large numbers. Therefore filtered water cannot be so thoroughly depended on as distilled water; consequently when filters are used, great care must be taken to change or cleanse the filtering substance frequently. The Pasteur or Chamberlain filter is the best. It will remove micro-organisms almost entirely from water. It is made of porous earthenware through which the water is filtered. The filter-tubes should be boiled frequently, to destroy all organized impurities in their pores.

Numerous small stills are upon the market that are adapted to family needs. These are much more reliable purifiers of water than niters and are no more difficult to use.

Waters are classified as soft or hard, according as they contain little, or no, or much, mineral matter in solution.

Rain-water is soft and more nearly resembles distilled water than any other natural water. When rain first falls it absorbs from the air certain germs and volatile acids that are at times present in it. If rain-water is collected, as it usually is, from roofs, it will contain also dirt that has lodged upon them. For this reason it is best to permit the rain that falls during short showers and during the first few minutes of heavy ones to escape, and to collect only that which falls later.

Certain spring-waters contain a minimum of mineral matter. The water of these springs does not pass through many strata of rock.

Soft waters are the most wholesome for consumption, but they are not always the most palatable. Hard waters frequently are relished better.

Mineral waters have been drunk for their medicinal effect since the savage days of man. Some have a pronounced physiologic action and others little or none. The benefit which invalids derive from a visit to a spa can rarely be obtained by drinking the same water at their homes. The freedom from care and hopefulness which absence from home generally insures, the change of diet, more exercise than usual in the open air are more important factors in influencing some cases than the mineral water. Invalids improve with so much greater certainty at the spa that many think the waters contain some volatile substance such as radium which is lost when the water is transported or stored. It is true that the latter element or some radioactive ingredient is found in many mineral waters. But how active therapeutically this agent in them is, has not been demonstrated.