(From altero, to change). Alteratives. Medicines of this kind claimed formerly a considerable share of the physician's attention, when acrimony was the most common reputed cause of diseases. This subject will be considered at length under the title of Pathology. It is sufficient at present to remark, that many of the supposed acrimonies have no existence, and the class of alteratives is consequently limited. We have, however, still the inspissants and attenuants, which, though they do not permanently affect the state of blood, yet change that of the excretory fluids; and so far, in a remote view, may be styled alterants. These are to be considered under their proper heads. Alteratives, in the present more scientific views of pathology and therapeutics, are those medicines supposed to correct the acrimony which appears in eruptions on the skin, formerly tailed the scorbutic acrimony. These are almost exclusively- mercurials, assisted by the medicines just spoken of under the article Alphus. They do not act by any chemical affinity on the mass of fluids, but by their power of gradually increasing the secretion from the skin; for we shall show, that cutaneous complaints are seldom owing to any increased acrimony, but sometimes to an obstructed cutaneous discharge; and, at others, to the excessive rapidity of this evacuation. The only instance of a real change in the circulating fluids, is in sea scurvy, and in high putrid fevers. The latter admit not of alteratives; and in the sea scurvy, the only useful medicine of this kind is a vegetable diet.

Alteratives have been given with other views, and seem occasionally to have some effect. We allude to the use of sea water in scrofula, to burnt sponge and mercurials in the same disease. In scrofula, there is evidently a want of irritability; and we may suspect a want also of a due proportion of neutral salts, which give fluidity to gluten, when dissolved in the serosity, forming the serum. This defect may occasion the stagnation of fluids in the conglobate glands, and we should be more confident in this explanation, were the contents of these glands gluten. The saline remedies, above mentioned, are undoubtedly useful, and probably act as attenuants; the mercurials are alterants by increasing the action of the vessels, deficient from the want of irritability. Emmenagogues and tonics are sometimes also considered as alterants, but with little accuracy. In fact, if there is any real medicine of this kind, it is mercury used in venereal complaints; to which we cannot deny some alterative power. It is proper, however, in this early part of our work, to declare our opinion, that it chiefly acts by exciting and supporting the evacuation from the skin.