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all. It is the most abundant substance of which we have knowledge. It
composes four-fifths of the weight of vegetables, and three-fourths of
that of animals. It is essential to the continuance of organic life.
Water is universally present in all of the tissues and fluids of the
body. It is not only abundant in the blood and secretions, but it is
also an ingredient of the solids of the body. According to the most
accurate computations, water is found to constitute from two-thirds to
three-fourths of the entire weight of the human body. The following
table, compiled by Robin and Verdeil, shows the proportion of water per
thousand parts in different solids and fluids:

QUANTITY OF WATER IN 1,000 PARTS.

Teeth, 100
Bones, 130
Cartilage, 550
Muscles, 750
Ligaments, 768
Brain, 789
Blood, 795
Synovial fluid, 805
Bile, 880
Milk, 887
Pancreatic juice, 900
Urine, 936
Lymph, 960
Gastric juice, 975
Perspiration, 986
Saliva, 995

THE NATURAL DRINK OF MAN. Water constitutes the natural drink of man. No
other liquid can supply its place. Its presence, however, in the body is
not permanent. It is discharged from the body in different ways; by the
urine, the feces, the breath, and the perspiration. In the first two, it
is in a liquid form, in the others in a vaporous form. It is estimated
that about forty-eight per cent. is discharged in the liquid, and
fifty-two per cent. in the vaporous form; but the absolute as well as
the relative amount discharged depends upon a variety of circumstances.

Water is never found perfectly pure, since it holds in solution more or
less of almost every substance with, which it comes in contact. Rain
falling in the country remote from habitations is the purest water that
nature furnishes, for it is then only charged with the natural gases of
the atmosphere. In cities it absorbs organic and gaseous impurities, as
it falls through the air, and flowing over roofs of houses carries with
it soot and dust. Water from melted snow is purer than rain-water, since
it descends in a solid form, and is therefore incapable of absorbing
gases. Rain-water is not adapted to drinking purposes, unless well
filtered. All water, except that which has be