self to
which it belongs. This holds good even after the blood has been long
dried.

Let us state before all what is to be understood by the smell of a
certain animal. There is the pure, specific smell of the animal,
inherent in its flesh, or, as we shall see hereafter, in certain
portions of its flesh. This smell is best perceived when the flesh is
gently boiling in water. The broth thereby obtained contains the
specific taste and smell of the animal--I call it specific, because
every species, nay every variety of species, has its own peculiar taste
and smell. Think of mutton broth, chicken broth, fish broth, &c. &c. I
shall call this smell, the specific scent of the animal. I need not say
that the scent of an animal is quite different from all such odours as
are generated within its organism, along with its various secretions and
excretions: bile, gastric juice, sweat, &c. These odours are again
different in the different species and varieties of animals. The
cutaneous exhalation of the goat, the sheep, the donkey, widely differ
from each other; and a similar difference prevails with regard to all
the other effluvia of these animals. In fact, as far as olfactory
experience goes, we may say that the odour of each secretion and
excretion of a certain species of animals is peculiar to itself, and
characteristically different in the similar products of another species.

By altering the food of an animal we may considerably alter all the
above-mentioned odours, scents, as well as smells; yet essentially they
will always retain their specific odoriferous type. All this is matter
of strict experience.

Strongly diffusive as all these odorous substances are, they permeate
the whole organism, and each of them contributes its share to what in
the aggregate constitutes the smell of the living animal. It is
altogether an excrementitious smell tempered by the scent of the animal.
That excrementitious smell we shall henceforth simply call the smell, in
contradistinction to the scent of the animal.

To return after this not very pleasant, but nevertheless necessary
digression, to our subject. Professor Yaeger found that blood, treated
by an acid, may emit the scent or the smell of the animal, according as
the acid is weak or strong. A strong acid, rapidly disintegrating the
blood, brings out the animal's smell; a weak acid, the animal's scent.

We see, then, that in every drop of blood of a certain species of
a