Thus it is that the system is rendered more susceptible of the influence of Mercury, by combining it with Antimony and Opium.[245] Where the stomach is insensible to impressions, the exhibition of Opium previous to, or in combination with, any active medicine, often assists its operation; this is remarkably striking in some states of mania, when emetics will fail, unless the stomach be previously influenced and prepared by a narcotic; indeed, in ordinary cases of inirritability of stomach, the addition of a small quantity of opium will often render an emetic active.[246] So again the system, when it is in that particular condition which is indicated by a hot and dry skin, is unsusceptible of the expectorant powers of Squill, unless it be in union with antimony or some powerful diaphoretic, (_Form. 134_.) Squill is by no means disposed to act upon the urinary organs, when exhibited singly; but calomel, and some other mercurial preparations,[247] when in conjunction with it, appear to direct its influence to the kidneys, and to render these organs more susceptible of its operation; (103, 106.) Upon the same principle, _Antimonial Wine_ quickens the operation of saline cathartics (69); _Opium_ increases the sudorific powers of _Antimony_ (124); and the purgative operation of _Jalap_ is promoted by _Ipecacuan_ (84). Dr. Aikin asserts that fifteen grains of the former purgative when combined with two or three grains of the latter root, will purge more than double that quantity of Jalap when administered without such an adjunct. Sir John Pringle speaks of the advantages which may be obtained by combining an alkali with a bitter infusion, by which the diuretic effects of the former will be increased, while the latter is calculated to remove any gastric debility, and to impart a general tone to the body: there is no doubt but that _Bitters_, from their invigorating influence upon the _primæ viæ_, (_see page 78_) increase the effects of remedies whose operation is connected with changes _in transitu_, or with absorption, as in the exhibition of certain diuretics;[248] they also frequently render the stomach and bowels more susceptible of bodies that act by impression, as purgatives, emetics, &c.