When it is known that something like four-fifths of the animal body consists of water, no argument will be necessary to prove the importance of a constant supply of the fluid in a proper condition for appropriation.

By the process of evaporation which is constantly going on from the skin, through the respiratory organs, and in other ways, water is constantly being excreted from the body, and when there is no supply from without to repair the loss, it must ultimately happen that all the animal tissues would become perfectly dried, which means that an animal weighing 100 lb. would be reduced to a mass weighing something under 30 lb. To compensate for the amount of water which is constantly being thrown off, even when in perfect rest, and to a much greater extent when undergoing exertion, it has been calculated that an adult man would require every twenty-four hours from ½ to 7/10 oz. of the fluid for each pound of his body weight. A man weighing 140 lb., therefore, will require from 70 to 90 oz. daily, and in ordinary English diet about 20 to 30 oz. of this is taken in the so-called solid food, and the remainder is drunk as liquid of some kind (Parkes). The horse, it is calculated, will require 8 to 12 gallons daily, a cow or small ox about 6 to 8 gallons, sheep or pigs ½ to 1 gallon (Parkes).

Colonel Fred. Smith states that from experiments made in 1866 the War Office fixed the daily supply for cavalry horses at 8 gallons, and artillery at 10 gallons per horse. This quantity, however, was to include all water used for stable purposes, and in the artillery was to include washing carriages. From Dr. Parkes's observation, however, this quantity would be quite insufficient, as he came to the conclusion that 16 gallons per day per horse for all purposes was not an excessive amount. Colonel Fred. Smith also remarks that in a stable of cavalry horses, doing very little work, and at a cool time of the year, the amount per horse was found to average 61/3 gallons; and from experiments which he made in India he found that during the month of February a horse consumed on an average 8½ gallons daily, which was made up as follows: Morning-water, 1.9 gallon; mid-day, 3-4 gallons; at evening, 3.15 gallons. It does not appear to have been ascertained how much water a horse would consume daily when water is kept constantly in the trough in the stable or box, but it is generally believed that a less quantity is taken than when the animal has the water supplied to him at intervals three times daily.