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124 DENTAL MEDICINE. ;

necessary, the capillaries diminish and disappear, so that the
cicatrix grows paler and of smaller bulk. In the case of an abra-
sion of the skin, the exuding plastic lymph dries upon the denuded
surface when not disturbed, and forms a protecting crust, which
at length falls off, exposing a reddish surface covered with epider-
mis. In the case of the oral mucous membrane, a like result is
produced under the protection of the mucous secretions peculiar
to such a tissue.
Suppuration.—Suppuration is the formation of pus, and is the
most frequent termination of acute inflammation, and is a process
by which the leucocytes and the embryonic cell formed from the
fixed tissue-cells are converted into pus-corpuscles and the inter-
cellular substance of the tissues undergoes liquefaction.
When pus forms an abscess, owing to some chemical substance
in its composition, it exerts a solvent action upon the tissues,
which is shown by the presence of broken-down tissue cells
and remains of tissue, mixed with pus-corpuscles. Suppuration is
directly caused by the action of certain specific micro-organisms,
and also by certain chemical irritants introduced under the skin.
The formation of pus is a result of destructive inflammation,
as the presence of such a fluid denotes a loss of substance, which
does not occur when a wound heals by the first intention. Under
favorable circumstances an inflamed surface, when destruction of
tissue has occurred, heals by the process of the second intention, as
follows : A soft, red surface of coagulable lymph becomes organ-
ized into embryonic tissue, which is known as granulation tissue.^
and the yellowish fluid, bland in nature, which is present, is pus
these materials, or" products of inflammation," being generated for
reparative processes. The granulation tissue is composed of em-
bryonic cells and a network of capillary loops, about which are
clustered a number of living leucocytes held together by a delicate
intercellular material, by which the tissue receives its supply of
nutritive matter from the blood, so that it may become what is
recognized later as the cicatricial tissue, or one of a higher organ-
ism than the granulation tissue. The healthy granulation tissue
is of a variable pinkish, or cherry-red color, the tint depending
upon the quality of the blood which its vessels contain, and is of