The _local_ effects are mainly of three kinds, viz., _corrosion_, or chemical decomposition, as is seen in the effects of the strong mineral acids and alkalies; _irritation_ or _inflammation_, varying from simple redness, in its mildest, to ulceration and gangrene, in its most severe degree, such as may result from the use of corrosive sublimate; and _a local specific effect_, produced on the sentient extremities of the nerves, as is felt on the local application of prussic acid, aconite, &c. The _remote_ effects are those influencing organs remote from the part to which the poison has been applied. These may be either common or specific; _common_, such as the constitutional indications of inflammatory fever, however produced; _specific_, like the constitutional effects of opium over and above its local influences in relieving pain, &c. Various narcotic poisons produce but little local change, though their remote effects are very remarkable. For example, belladonna, in whatever way it may be introduced into the system, paralyzes the ciliary nerves and so causes dilatation of the pupil. Many substances have both a local and remote action, as is well seen in the influence of cantharides upon the part to which they are applied, and their remote effects upon the urinary organs. These remote effects must be induced by one of two modes, or, as some contend, by both: by _absorption_, that is, by the passage of the poisonous particles into the blood; or by _sympathy_, that is, by an impression transmitted through the nerves.