Vegetable substances alone will not sustain life for a great length of
time in every climate, but there is a vast difference between the wants of
man at the equator and his necessities at the pole.
Nature requires for the working of her plans materials of diverse natures:
neither the oil, nor starch, nor sugar, will sustain life alone. Chemical
analysis and physiological history point out to us how positive is the
law which fixes the component parts of grains and plants, and how
imperative the necessity of adjusting in alimentation these forms of
nutritive matter, which spring up on every side in profusion, and offer
endless variety to the wants of man.
There must be harmony of certain principles; there must be union of
starch, of gluten, and fat, to complete the process of digestion and
assimilation. To feed a patient upon arrow-root, tapioca, or sago, and the
like, is to consign him to certain death. Instinct impels us sometimes to
make use of articles which our habits have thrown aside.