so an appreciable amount, one per cent or
more, in all the tissues. Ash is exceedingly variable in composition,
being composed of the various salts of potassium, sodium, calcium,
magnesium, and iron, as sulphates, phosphates, chlorides, and silicates
of these elements. There are also other elements in small amounts. In
the plant economy these elements take an essential part and are
requisite for the formation of plant tissue and the production in the
leaves of the organic compounds which later are stored up in the seeds.
Some of the elements appear to be more necessary than others, and
whenever withheld plant growth is restricted. The elements most
essential for plant growth are potassium, calcium, magnesium, iron,
phosphorus, and sulphur.[1]

In the animal body minerals are derived, either directly or indirectly,
from the vegetable foods consumed. The part which each of the mineral
elements takes in animal nutrition is not well understood. Some of the
elements, as phosphorus and sulphur, are in organic combination with the
nitrogenous compounds, as the nucleated albuminoids, which are very
essential for animal life. In both plant and animal bodies, the mineral
matter is present as mineral salts and organic combinations. It is held
that the ash elements which are in organic combination are the forms
mainly utilized for tissue construction. While it is not known just what
part all the mineral elements take in animal nutrition, experiments show
that in all ordinary mixed rations the amount of the different mineral
elements is in excess of the demands of the body, and it is only in rare
instances, as in cases of restricted diet, or convalescence from some
disease, that special attention need be given to increasing the mineral
content of the ration. An excess of mineral matter in foods is equally
as objectionable as a scant amount, elimination of the excess entailing
additional work on the body.

The composition of the ash of different food materials varies widely,
both in amount, and form of the individual elements. When for any reason
it is necessary to increase the phosphates in a ration, milk and eggs do
this to a greater extent than almost any other foods. Common salt, or
sodium chloride, is one of the most essential of the mineral
constituents of the body. It is necessary for giving the blood its
normal composition, furnishing acid and basic constituents for the
production of the digestive fluids, and for the nutriti