hich they
are applied. The class includes mineral, animal, and vegetable
substances, and contains a larger number of poisons than all the other
classes together. Irritants may be divided into two groups: (1) Those
which destroy life by the irritation they set up in the parts to which
they are applied; (2) those which add to local irritation peculiar or
specific remote effects. The first group includes the principal
vegetable irritants, some alkaline salts, some metallic poisons, etc.;
and the second comprises the metallic irritants, the metalloids
(phosphorus and iodine), and one animal substance, cantharides.

_Symptoms._--Burning pain and constriction in throat and gullet, pain
and tenderness of stomach and bowels, intense thirst, nausea, vomiting,
purging and tenesmus, with bloody stools, dysuria, cold skin, and feeble
and irregular pulse. The vomit consists at first of the food, then it
becomes bile-stained, and later dark coffee-grounds in appearance, due
to extravasation of blood from the over-distended vessels in the gastric
mucous membrane. Death may occur from shock, convulsions, collapse,
exhaustion, or from starvation on account of chronic inflammation of the
gastro-intestinal mucous membrane.

_Post-Mortem Appearances._--Those of inflammation and its consequences.
Coats of stomach, fauces, gullet, and duodenum, may be thickened,
black, ulcerated, gangrenous, or sloughing. Vessels filled with dark
blood ramify over the surface. Acute inflammation is often found in the
small intestines, with ulceration and softening of mucous membrane. The
rectum is frequently the seat of marked ulceration.

3. =Poisons Acting on the Brain.=--Three classes: The opium group,
producing sleep; the belladonna group, producing delirium and illusions;
and the alcohol group, causing exhilaration, followed by delirium or
sleep.

_Symptoms._--Of the opium group, giddiness, headache, dimness of sight,
contraction of the pupils, noises in the ears, drowsiness and confusion,
passing into insensibility. Of the belladonna group, delirium, illusions
of sight, dilated pupils, dry mouth, thirst, redness of skin, coma. Of
the alcohol group, excitement of circulation and of cerebral functions,
want of power of co-ordination and of muscular movement, double vision,
mania, followed by profound sleep and coma. In the chronic form,
delirium tremens.

_Post-Mortem Appearances._--In the opium group, fulness of the sinuses
and veins of the brain,