ounds contained
in the food already contain exactly the amount of carbon which is
required for the production of fibrine and albumen. Now, it can be shown
that very little of the excess of this carbon is ever expelled in the
form either of solid or liquid compounds; it must be expelled,
therefore, in the gaseous state. In short, these compounds are solely
expended in the production of animal heat, being converted by the oxygen
of the air into carbonic acid and water. The food of carnivorous animals
does not contain non-nitrogenised matters, so that the carbon and
hydrogen necessary for the production of animal heat are furnished in
them from the waste of their tissues.

The transformed matters of the organs are obviously unfit for the
further nourishment of the body--that is, for the increase or
reproduction of the mass. They pass through the absorbent and lymphatic
vessels into the veins, and their accumulation in these would soon put a
stop to the nutritive process were it not that the blood has to pass
through a filtering apparatus, as it were, before reaching the heart.
The venous blood, before returning to the heart, is made to pass through
the liver and the kidneys, which separate from it all substances
incapable of contributing to nutrition. The new compounds containing the
nitrogen of the transformed organs, being utterly incapable of further
application in the system, are expelled from the body. Those which
contain the carbon of the transformed tissues are collected in the
gall-bladder as bile, a compound of soda which, being mixed with water,
passes through the duodenum and mixes with chyme. All the soda of the
bile, and ninety-nine-hundredths of the carbonaceous matter which it
contains, retain the capacity of re-absorption by the absorbents of the
small and large intestines--a capacity which has been proved by direct
experiment.

The globules of the blood, which in themselves can be shown to take no
share in the nutritive process, serve to transport the oxygen which they
give up in their passage through the capillary vessels. Here the current
of oxygen meets with the carbonaceous substances of the transformed
tissues, and converts their carbon into carbonic acid, their hydrogen
into water. Every portion of these substances which escapes this process
of oxidation is sent back into the circulation in the form of bile,
which by degrees completely disappears.

It is obvious that in the system of the graminivo