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 after injury, and certain of the changes are only an accentuation of those which take place in the usual life; but others, such as the formation of the exudate, are unusual; not only is the outpouring of fluid greatly increased, but its character is changed.

In the normal transudation[2] the substances on which the coagulation of the blood depends pass through the vessel wall to a very slight extent, but the exudate may contain the coagulable material in such amounts that it easily clots.

The interchange between the fluid outside the vessels and the blood fluid takes place by means of filtration and osmosis.