This term designates any irritation artificially established, with a view to diminish, counteract, or remove some other irritation or inflammation existing in the body. (Dr. Williams.) The substances employed in establishing this state are called counter-irritants, and may be divided into - 1. Rubefacients. 2. Pustular counter-irritants, as Tartar Emetic.

3. Vesicants, Or Blisters

4. Issues and Setons. 5. Caustics, or Escharotics. Each of these is considered under its respective head. They are chiefly applicable to chronic diseases; but there are cases when vesicants or blisters prove in the highest degree useful in acute diseases, the first inflammatory symptoms having been subdued by depletion, &c.

The extent and form of counter-irritation should, in a great measure, be regulated by the character of the disease or lesion which it is intended to cure: thus a rubefacient is chiefly indicated in irritation of mucous membranes; a vesicant, in inflammation of serous membranes; and a seton or issue, when the disease is of a suppurative character.

Therapeutic Uses. These are enumerated fully in the articles Blisters, Issues and Setons, &c.

3050. Derivants are agents employed to produce an artificial hyperAemia in some part of the body distant from the seat of an existing hyperAemia. Under this head, therefore, may be included several forms of counter-irritation already noticed; but, in addition, there are two important modes of derivation to be referred to - viz., Dry-cupping and the application of Junod's Exhausting Apparatus.

3051. In Intermittent Fevers, M

Gondret* states, that in his private practice, during a period of twenty-seven years, he has never once met with a case of Ague which has not yielded to dry-cupping along the spine. He gives the following directions for its use: - Apply eight or ten middle-sized cupping-glasses on each side of the spinal column, on the neck downwards, and let them remain on for thirty or forty minutes. The time for applying the cups is the beginning of the cold stage, or, if it be possible, a short time before its accession. This not only prevents the attack, but, at the same time, the hot fit and the sweating. In most cases, one application of the cups is sufficient to effect a cure; but, in long-standing cases, it requires to be repeated three or four times. This simple remedy deserves a further trial.

3052. To Poisoned Wounds, whether from Snakes or other sources, the application of cupping-glasses (dry-cupping) over the affected part is one of the surest and best means of preventing the ill effects which would otherwise probably ensue. The valuable experiments of Sir David Barry place this beyond a doubt. Several dogs and rabbits were bitten by vipers. To the bites of some he applied the cupping-glass; to the bites of others, nothing. When the glass was applied for half an hour to such as had been bitten by one, two, or even three vipers, no symptom whatever of constitutional disturbance appeared; whilst those which were left to nature were invariably attacked with convulsions and stupor: none of them, however, died. From these experiments he draws the following inferences: - 1. That neither sound nor wounded parts of the surface of a living animal can absorb when placed under a vacuum. 2. That the application of the vacuum by means of a piston cupping-glass arrests or mitigates the symptoms caused by the poison. 3. That the application of a cupping-glass for half an hour deprives the vessels of the part over which it is applied of their absorbent faculty for an hour or two after the removal of the glass. 4. That this measure is rendered, in a great measure, inoperative if extensive scarifications have been made in the neighbourhood of the original wound.