er quantities
in early life, while the bone is undergoing development, than
afterwards. In childhood the bones are composed largely of animal
matter, being pliable and easily moulded. For this reason the limbs of
young children bend under the weight of their bodies, and unless care is
taken they become bow-legged and distorted. Whenever there is a
continued deficiency of the earthy constituents, disease of the bones
ensues. Therefore, during childhood, and particularly during the period
of dentition, or teething, the food should be nutritious and at the same
time contain a due proportion of lime, which is preferable in the form
of a phosphate. When it cannot be furnished by the food, it should be
supplied artificially. Delayed, prolonged, and tedious dentition
generally arises from a deficiency of lime.

With the advance of age it accumulates, and the bone becomes hard,
inelastic, and capable of supporting heavy weights. Farther on, as in
old age, the animal matter of bone becomes diminished, and lime takes
its place, so that the bones become brittle and are easily broken. Lime
exists largely in hard water, and to a greater or less extent in milk,
and in nearly all foods except those of an acid character.

_Phosphorus_ exists in various combinations in different parts of the
body, particularly in the brain and nervous system. Persons who perform
a large amount of mental labor require more phosphorus than those
engaged in other pursuits. It exists largely in the hulls of wheat, in
fish, and in eggs. It should enter to a considerable extent into the
diet of brain workers, and the bread consumed by them should be made of
unbolted flour.

_Sulphur, Iron, Soda_, and _Potash_ are all necessary in the various
tissues of the body, and deficiency of any one of them, for any
considerable length of time, results in disease. They are all supplied,
variously arranged and combined, in both animal and vegetable food; in
some articles they exist to a considerable extent, in others in much
smaller quantities. _Sulphur_ exists in eggs and in the flesh of
animals, and often in water. _Iron_ exists in the yolk of eggs, in
flesh, and in several vegetables. _Soda_ is supplied in nearly all food,
and largely in common salt, which is a composition of sodium and
hydrochloric acid, the latter entering into the gastric juice. _Potash_
exists, in some form or other, in sufficient quantities for health, in
both vegetable and animal food.

CLAS