Sinapism, signifies an external application, in the form of a soft plaster, or poultice, for the same purposes as a Blister, to which we refer.

The most usual si: is composed of equal parts of mustard-flower and crumbs of bread, mi with such a proportion of vinegar as will render it of a proper consistence to be spread on linen, or cotton. In this state, the preparation is to be applied to the skin, till the latter become red and painful. The time required for producing such effect, is very unequal. In irritable persons, it will sometimes ate within 15 minutes ; while, in others, it may continue on the part to be stimulated for 0 or 8 hours, without occasioning considerable uneasiness. If, however, the cataplasm be suffered to re main in its place, for some time after the commencement of the pain, it will draw a blister, which must be treated in a manner similar to that occasioned by the Spanish-Fly. (See vol. ii. p. 310.) But, if it be intended to operate by a gradual discharge of matter, or Serum, (seeBlood) the red or sore part may be kept in a moist state, by the repeated application of cabbage-leaves; and, according to circumstances, the sinapism may be renewed on the same spot.

The size of such blistering plasters depends on that of the individual, and the nature of the affection : thus, in children, they need not be larger than one, or at the farthest, two inches in di but, in adults, they may ally be spread to the extent of from throe to six inches and upwards, though of less breadth in proportion to their length. - The most usual parts of the body, on which these external remedies are calculated to produce speedy relief, are the calves of the legs, and the soles of the feet} especially with a view to abate pain arising from internal inflammations; to draw catarrhal and rheumatic humours from parts essential to life, towards the lower extremities ; and to determine the morbid matter in the small-pox, so as to affect the face with less severity. - In rheumatic tooth and head-achs, the sinapism ought to be applied either to the nape of the neck, or to one of the upper arms ; in inflammations of the chest, between the shoulder-blades ; in apoplectic cases, to the neck, calves of the legs, and soles of the feet; in malignant putrid or nervous fevers, to the arms, thighs, legs, &;c. - These domestic remedies are, in the instances before enumerated, of greater service than is generally supposed; and we are convinced from experience, that in the plurality of cases, they are infinitely more proper, safe, and efficacious, than the common blisters of the shops.