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114 DENTAL MEDICINE. —

convulsions attending difficult dentition, the irritation being com-
municated to the brain by the fifth pair of nerves, and from
thence to the nerves of the voluntary muscles, the seat of the
spasmodic action. Dental caries also affords another example of
indirect irritation, in the form of neuralgic pains of the temple,
face, ear, eye, and of even more remote parts, such as the uterus.
The effect of irritation upon the vascular system is manifested
by dilatation of the blood vessels; but the immediate effect, how-
ever, of a slight chemical or mechanical irritant is not at once
apparent in the capillaries, but first causes contraction of the
smaller arteries, and sometimes of the veins, such contraction
being followed by a dilatation, the immediate cause of which is
yet obscure. It is, however, supposed to be the result of relaxa-
tion or a temporary paralysis of the walls of the vessels, a con-
dition following contraction, and which, as a consequence, causes
a decrease of their resistance to the pressure of the blood within
them. The irritation either perverts the function of the nerves
of the vessels, or of the lining cell substance of the capillary
walls; or the disturbance is due to reflex action.
Inflammation denotes an abnormal process or condition
characterized by certain changes of texture, which, although uni-
form in type differ widely in appearance, and terminate in dif-
ferent results, according to the nature and permanency of the
causes upon which such a condition depends, or which have
given rise to it.
The symptoms of inflammation consist of the phenomena which
accompany the textural changes characteristic of this condition,
and its pathology the textural changes which occur during the
continuance of this condition. The essential features of inflam-
mation are an increased afflux of blood to the affected part, with
a greatly increased tendency to cell proliferation and tissue for-
mation.
The causes of inflammation determine in a great degree its
treatment on account of the influence they exert upon its de-
structive tendencv, and they may be classified as those arising
1st, from mechanical violence ; id, from irritating and destruc-
tive chemical action ; 3d, from poisonous infection, and the