supply of water enables the food to be dissolved or suspended in it,
and in solution the food material is easily distributed to all parts
of the body.

Further, water assists in the removal of the daily bodily wastes, and
thus rids the system of foul and poisonous substances.

The human body itself consists largely of water; indeed, about two
thirds of our own weight is water. The constant replenishing of this
large quantity is necessary to life, and a considerable amount of the
necessary supply is furnished by foods, particularly the fruits and
vegetables.

But while the supply furnished by the daily food is considerable, it
is by no means sufficient, and should be supplemented by good drinking
water.

69. Water and its Dangers. Our drinking water comes from far and
near, and as it moves from place to place, it carries with it in
solution or suspension anything which it can find, whether it be
animal, vegetable, or mineral matter. The power of water to gather up
matter is so great that the average drinking water contains 20 to 90
grains of solid matter per gallon; that is, if a gallon of ordinary
drinking water is left to evaporate, a residue of 20 to 90 grains will
be left. (See Laboratory Manual.) As water runs down a hill slope
(Fig. 37), it carries with it the filth gathered from acres of land;
carries with it the refuse of stable, barn, and kitchen; and too often
this impure surface water joins the streams which supply our cities.
Lakes and rivers which furnish drinking water should be carefully
protected from surface draining; that is, from water which has flowed