328
OP DIGESTION IN GENERAL.
SECTION I.
OF DIGESTION, CHYLIFICATION, AND THE EXCRETION OF THE DECOM¬
POSED EFFETE MATTERS!
CHAPTER I.
Of Digestion in General.
The food of animals consists of animal and vegetable substances.
Some animals live solely on the former class of substances, others on
the latter; others, again, amongst which is man, have a mixed diet,
consisting of both animal and vegetable matters. Man is supported
as well by food constituted wholly of animal substances as by that
which is formed entirely of vegetable matters; and the structure of
his teeth, as well as experience, seems to point out that he is destined
for a mixed kind of aliment.
Both the vegetable and animal articles of diet contain the more
common salts, which, being essential components of the animal sys¬
tem, may in a certain point of view be regarded as nutriment. But
no animal can. subsist on mineral substances alone; though from
necessity, or from prejudice, for the purpose of filling the stomach,
earth, either alone or mixed with organic matters, is sometimes
swallowed by human beings,—for instance, by the Ottomaks and
Guamos in Oronoco, and by the inhabitants of New Caledonia.
Vauquelin could detect no nutritious matter in the steatite which is
eaten by the inhabitants of New Caledonia.* The earth, which, on
account of famine, was, in the year 1832, in the parish of Degernä,
on the borders of Lapland, mixed with flour and the bark of trees,
and baked so as to form a kind of bread, consisted of siliceous earth
mixed with organic particles. (Poggendorf’ s Jinn. B. xxix. p. 261.)
This mineral flour was found by Retzius to consist of the fossil re¬
mains of nineteen different forms of infusoria.
All substances from the animal and vegetable kingdoms appear to
afford nutriment, provided that they are easily soluble in the animal
fluids, contain no combination of elements too unlike that of the ani¬
mal matters of the being which they ought to nourish, possess no
remarkable chemical properties, and have no tendency to enter into
binary combinations at the expense of the organic components of
the living body. Substances which have such a tendency, which
are of heterogeneous composition, or have peculiar chemical proper¬
ties, are either medicinal substances, or, in a relative sense, poisons.
I am much inclined to believe that even the peculiar effects of the
narcotic poisons which produce no evident material change in the
system, and do not essentially excite inflammation, arise from the
* See Humboldt’s Reise in den Equinoct. Gegend, iv. p. 557. Travels in the
Equinoctial Regions of the New Continent, translated.—Rudolphi’s Physiol, ii. 18.