t a much greater amount of the same substance in dilute
solution causes no irritation. The poisonous substances produced by
bacteria are diluted and washed away from the part by the exudate. Not
only is there a greater amount of tissue fluid in the inflamed part,
but the circulation of this is also increased, as is shown by
comparing the outflow in the lymphatic vessels with the normal. The
fluid exudate which has come from the blood and differs but slightly
from the blood fluid exerts not only the purely physical action of
removing and diluting injurious substances, but in many cases has a
remarkable power, exercised particularly on bacterial poisons, of
neutralizing poisons or so changing their character that they cease to
be injurious.

We have learned, chiefly from the work of Metschnikoff, that those
white corpuscles or leucocytes which migrate from the vessels in the
greatest numbers have marked phagocytic properties, that is, they can
devour other living things and thus destroy them just as do the
amoebae. In inflammations produced by bacteria there is a very active
migration of these cells from the vessels; they accumulate in the
tissue and devour the bacteria. They may be present in such masses as
to form a dense wall around the bacteria, thus acting as a physical
bar to their further extension. The other form of amoeboid cell, which
Metschnikoff calls the macrophage, has more feeble phagocytic action
towards bacteria, and these are rarely found enclosed within them. It
is chiefly by means of their activity that other sorts of substances
are removed. They often contain dead cells or cell fragments, and when
haemorrhage takes place in a tissue they enclose and remove the
granules of blood pigment which result. They often join together,
forming connected masses, and surround such a foreign body as a hair,
or a thread which the surgeon places in a wound to close it. They may
destroy living cells, and do this seemingly when certain cells are in
too great numbers and superfluous in a part, their action tending to
restore the cell equilibrium. The foreign cells do even more than
this: they themselves may be devoured by the growing cells of the
tissue, seemingly being actuated by the same supreme idea of sacrifice
which led Buddha to give himself to the tigress.

The explanation of most of the changes which take place in
inflammation is obvious. It is a definite property of all living
things that repair takes place