osis into another kind of substance. To prove that the
number of these changes is bounded by no narrow limits, I need but refer
to the rules of Permutation, which demonstrate that twelve letters of
the alphabet may be arranged in no fewer than 479,000,000 different
ways.[1] The elements are the letters of Nature's alphabet, their
compounds are the words of the language of Creation. The combinations
of sounds and of signs which express the ideas and sensations of man may
be limited to millions; but numberless are the hieroglyphs by which the
Divine wisdom and beneficence is inscribed on the pages of the
magnificent volume of Nature.

Of the sixty-six elementary bodies, not more than a dozen occur
commonly in animal and vegetable substances; these are Oxygen, Hydrogen,
Nitrogen, Carbon, Sulphur, Phosphorus, Chlorine, Silicium, Potassium,
Sodium, Calcium, Magnesium, and Iron. In addition to these, Iodine, and
sometimes Bromine, are found in plants which grow in or near the sea;
and the former element has also been detected in some of the lower
animals, and in land plants. Manganese, Lithium, Caesium, Rubidium,
and a few others of the simple bodies, occasionally occur in plants and
animals, but I believe their presence therein is always accidental.

_Proximate Composition of Animal Substances._--The differences between
vegetable and animal substances are often more apparent than real.
Indeed many of the more important of these substances are almost
identical in composition. The albumen which coagulates when the juices
of vegetables are boiled, is identical with the albumen of the white
of eggs; the fibrine of wheat is in no respect chemically different
from the fibrine, or clot, of the blood; and, lastly, the legumine,
or _vegetable caseine_, of peas is almost indistinguishable from the
curd of milk, or _animal caseine_. But not only has chemical research
demonstrated the identity of the albumen, fibrine, and caseine of
vegetables with three of the more important constituents of animals, it
has gone a step further, and proved that they differ from each other in
but a few unimportant respects. They are unquestionably convertible into
each other[2] within the animal organism; and their functions, as elements
of nutrition, are almost, if not quite, identical.

Exclusive of the blood, which contains the elements of every part of
the body, the animal organism is composed of three distinct classes of
substances--namely, _nitrog