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OF THE ORGANIC SYSTEM. 99
long. In the capillaries she finds tissues which want
oxygen more than she ; she gives it up, loads herself
with carbonic acid, and returns, slowly, dark, and mourn
ful to the heart, again to be rid of her burden, and
again to .brighten under the vitalizing oxygen.
The action of the blood in the capillaries is obscure.
We know that it turns from arterial to venous, changing
its color from scarlet to purple. We know that it loses
oxygen, and receives carbonic acid. We know that
new matter is deposited in the tissues by cellular appro
and that the waste matter is removed. We
priation,
know that in this process there is an evolution of ani
mal heat. We know that all this takes place under the
influence of the nervous system: and directly, we be
lieve, under that of the nerves of organic life. I be
lieve, moreover, that in every minutest part, this nervous
power is endued with an adaptive intelligence, which
provides, to a great extent, and as far as possible,
Of this more es
against all accidents and exigencies.
pecially hereafter.
And now the blood, having eaten its food, and breathed
its air, and performed its work in the capillaries, where
it builds up with new, and whence it conveys whatever
rubbish of the old, must be relieved of its burden, and
kept sweet, pure, and vigorous, that it may give sweet
ness, purity, and vigor to all parts of the system, and
especially to the brain and especial organs of the soul,
to which it first and chiefly ministers.
For this purpose, we have a set of depurating or
cleansing organs. Some of these have been already
noticed. The foecal matter is poured from the blood
vessels in the mucous membrane of the intestines,