mach, kidneys and heart). In certain abnormal conditions, the
body's water supply is depleted. This is particularly true in the case
of hemorrhage, vomiting, and diarrhea. Under other conditions (certain
types of nephritis), the body becomes overburdened through the excess
of water retained, owing to the difficulty which the kidneys show in
eliminating it. This retention of water by the tissues gives rise to
the condition known as edema.

MINERAL SALTS

~Ash.~--The eight remaining chemical elements, _i.e._, calcium,
magnesium, sulphur, iron, sodium, potassium, phosphorus, chlorine,
constituting the mineral salts or ash, are likewise classed as food on
account of the work which they perform in the body. Some of these
elements enter the body as essential constituents of the organic
compounds, and are metabolized in the body as such, becoming inorganic
only upon oxidation of the organic materials of which they form a
part.

~Importance of the Mineral Salts.~--The way in which the mineral
elements exist in the body and take part in its functions, has been
graphically outlined by Sherman as follows.

"(1) As bone constituents, giving rigidity and relative permanence to
the skeletal tissues. (2) As essential elements of the organic
compounds which are the chief solids of the soft tissues (muscles,
blood cells, etc.). (3) As soluble salts (electrolytes) held in
solution in the fluids of the body; giving to those fluids their
characteristic influence upon the elasticity and irritability of
muscle and nerve; supplying material for the acidity and alkalinity of
the digestive juices and other secretions; and yet maintaining the
neutrality, or slight alkalescence, of the internal fluids as well as
their osmotic pressure and solvent power."[9]

The above outline, showing the various ways in which the mineral
constituents enter and take part in the various functions, as well as
in the structure of the body, make it evident that the same close
attention and study which was given to the other foodstuffs must be
accorded to these substances. When the student realizes that the
presence of certain salts dissolved in the blood assists in the
regulation of the vital processes of the body such as the digestion,
circulation and respiration; that they are responsible for the
contraction and relaxation of the muscles; that they assist in
controlling the nerves; that they are, in a way, instrumental in
releasing the energy locked up in