on, strictly so called, that is, for the
production of blood; substances which may be entirely dispensed with
in their nourishment in the adult state. In the young of carnivorous
birds, the want of all motion is an obvious cause of diminished
waste in the organised parts; hence, milk is not provided for them.

The nutritive process in the carnivora thus presents itself under
two distinct forms; one of which we again meet with in the
graminivora.

In graminivorous animals, we observe, that during their whole life,
their existence depends on a supply of substances having a
composition identical with that of sugar of milk, or closely
resembling it. Everything that they consume as food contains a
certain quantity of starch, gum, or sugar, mixed with other matters.

The function performed in the vital process of the graminivora by
these substances is indicated in a very clear and convincing manner,
when we take into consideration the very small relative amount of
the carbon which these animals consume in the nitrogenised
constituents of their food, which bears no proportion whatever to
the oxygen absorbed through the skin and lungs.

A horse, for example, can be kept in perfectly good condition, if he
obtain as food 15 lbs. of hay and 4 1/2 lbs. of oats daily. If we
now calculate the whole amount of nitrogen in these matters, as
ascertained by analysis (1 1/2 per cent. in the hay, 2.2 per cent.
in the oats), in the form of blood, that is, as fibrine and albumen,
with the due proportion of water in blood (80 per cent.), the horse
receives daily no more than 4 1/2 oz. of nitrogen, corresponding to
about 8 lbs. of blood. But along with this nitrogen, that is,
combined with it in the form of fibrine or albumen, the animal
receives only about 14 1/2 oz. of carbon.

Without going further into the calculation, it will readily be
admitted, that the volume of air inspired and expired by a horse,
the quantity of oxygen consumed, and, as a necessary consequence,
the amount of carbonic acid given out by the animal, are much
greater than in the respiratory process in man. But an adult man
consumes daily abut 14 oz. of carbon, and the determination of
Boussingault, according to which a horse expires 79 oz. daily,
cannot be very far from the truth.

In the nitrogenised constituents of his food, therefore, the horse
receives rather less than the fifth part of the carbon which his
organism requires for the support of the respiratory