CHAPTER II.

The Nutritive Value of Bengal Jail Dietaries.

"We live not upon what we eat, but upon what we digest."

     The chief uses of food are:— first, to form the tissues of the body and repair
the waste of every-day wear and tear; secondly, to furnish energy for the muscular
and other work that the body has to perform and to yield heat to keep the body
temperature at a proper constant level.

      We have already seen that a diet may be considered from two points of view,
viz.: its power or capability of forming new tissues or repairing waste—this
depends principally on its assimilable or available nitrogenous material; its power
of yielding energy and heat—this is a function of the protein, carbohydrate and
fat of the diet.

     The real nutritive value of a diet depends not simply on the proportions of
nutrients which it contains, but on the amount of those nutrients which can be
made available to the body by digestion for the building-up and repair of the
tissues and for the yielding up of energy. Therefore, in the study of a diet it will
be sufficient—so far as its nutritive value is concerned—to estimate the amount
of nitrogenous material that undergoes metabolism in the body and compare this
with the quantity offered in the diet, and then estimate the potential energy
available in the food compared with the energy given off by the body as heat or
mechanical work. With regard to the amount of energy transformed in the body
on the jail diets under investigation, we have no experimental evidence to produce,
and shall, therefore, have to rely on the generally accepted standards of the re-
quirements of the body for fuel, contrasting these standards with the amount of
energy available in the dietaries.

     The first and more important part of the problem we shall now take up,
giving as concisely as possible the results obtained from investigations on pri-
soners on the ordinary jail dietaries and on modifications of those dietaries.

      In order to render the work done on the nitrogenous metabolism of prisoners
intelligible we shall follow the following scheme in stating our results:—

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