sses the power of forming from the
constituents of its blood the substance of its membranes and cellular
tissue, of the nerves and brain, of the organic part of cartilages and
bones. But the blood must be supplied to it ready in everything but its
form--that is, in its chemical composition. If this is not done, a
period is put to the formation of blood, and, consequently, to life.

The whole life of animals consists of a conflict between chemical forces
and the vital power. In the normal state of the body of an adult these
stand in equilibrium: that is, there is equilibrium between the
manifestations of the causes of waste and the causes of supply. Every
mechanical or chemical agency which disturbs the restoration of this
equilibrium is a cause of disease.

Death is that condition in which chemical or mechanical powers gain the
ascendancy, and all resistance on the part of the vital force ceases.
This resistance never entirely departs from living tissues during life.
Such deficiency in resistance is, in fact, a deficiency in resistance to
the action of the oxygen of the atmosphere.

Disease occurs when the sum of vital force, which tends to neutralise
all causes of disturbance, is weaker than the acting cause of
disturbance.

Should there be formed in the diseased parts, in consequence of the
change of matter, from the elements of the blood or of the tissue, new
products which the neighbouring parts cannot employ for their own vital
functions; should the surrounding parts, moreover, be unable to convey
these products to other parts where they may undergo transformation,
then these new products will suffer, at the place where they have been
formed, a process of decomposition analogous to putrefaction.

In certain cases, medicine removes these diseased conditions by exciting
in the vicinity of the diseased part, or in any convenient situation, an
artificial diseased state (as by blisters), thus diminishing by means of
artificial disturbance the resistance offered to the external causes of
change in these parts by the vital force. The physician succeeds in
putting an end to the original diseased condition when the disturbance
artificially excited (or the diminution of resistance in another part)
exceeds in amount the diseased state to be overcome.

The accelerated change of matter and the elevated temperature in the
diseased part show that the resistance offered by the vital force to the
action of oxygen is feebler t