#Sequence of Changes in Bacterial Inflammation.#--As the form of
inflammation with which we are most concerned is that due to the action
of bacteria, in describing the process by which the protective influence
of the inflammatory reaction is brought into play, we shall assume the
presence of a bacterial irritant.

The introduction of a colony of micro-organisms is quickly followed by
an accumulation of wandering cells, and proliferation of
connective-tissue cells in the tissues at the site of infection. The
various cells are attracted to the bacteria by a peculiar chemical or
biological power known as _chemotaxis_, which seems to result from
variations in the surface tension of different varieties of cells,
probably caused by some substance produced by the micro-organisms.
Changes in the blood vessels then ensue, the arteries becoming dilated
and the rate of the current in them being for a time increased--_active
hyperæmia_. Soon, however, the rate of the blood flow becomes slower
than normal, and in course of time the current may cease (_stasis_), and
the blood in the vessels may even coagulate (_thrombosis_). Coincidently
with these changes in the vessels, the leucocytes in the blood of the
inflamed part rapidly increase in number, and they become viscous and
adhere to the vessel wall, where they may accumulate in large numbers.
In course of time the leucocytes pass through the vessel
wall--_emigration of leucocytes_--and move towards the seat of
infection, giving rise to a marked degree of _local leucocytosis_.
Through the openings by which the leucocytes have escaped from the
vessels, red corpuscles may be passively extruded--_diapedesis of red
corpuscles_. These processes are accompanied by changes in the
endothelium of the vessel walls, which result in an increased formation
of lymph, which transudes into the meshes of the connective tissue