_Saline Diaphoretics_, as they readily pass with the chyle, may be supposed to enter the circulation, and be thus brought to act, directly, on the cutaneous vessels; at the same time it seems extremely probable that such remedies may also occasion an impression on the stomach, which is sympathetically communicated to the vessels of the skin; they have undoubtedly little or no influence on the general vascular system, and neither augment the force nor the velocity of the circulating current. It is not, however, in febrile affections alone that this class of remedies proves highly beneficial; the very intimate sympathetic connection which subsists between the functions of the lungs and skins, renders the use of such medicines particularly advantageous in the cure of the diseases incident to the former of these organs; a fact upon which we shall hereafter offer some remarks under the history of _Expectorants_. So again, in the treatment of bowel affections, in consequence of the intimate relation which exists between the cutaneous capillaries and those of the internal organs, gentle diaphoretics offer a valuable resource in their cure. How frequently do Diarrhæa, Enteritis, &c. ensue from the sudden suppression of perspiration by cold? From the influence which these medicines exert upon the extreme vessels of the skin, they are also highly serviceable in various obstinate cutaneous affections, as _Herpes_, _Lepra_, &c. As evacuating the serous part of the blood must necessarily have an indirect effect in promoting absorption, _Sudorifics_ have been occasionally exhibited in Dropsy, especially in that form of the disease called _Anasarca_. It has been already observed that cases too frequently occur in which the discharge of urine cannot be increased by art; upon such occasions practitioners have sometimes had recourse to a trial of Sudorifics,[165] but from the great difficulty which generally exists in exciting sweating in such affections, the indication has rarely been fulfilled. Where however a sudorific does succeed, it is less liable to debilitate than the other alternative of a drastic purgative. There is still another point of view in which the therapeutic importance of Diaphoretics may be considered. It is generally acknowledged that by cutaneous transpiration a portion of excrementitious matter is ejected from the system; hence by the failure or imperfect performance of this function, a deleterious fluid is retained which may give origin to disease; to such a cause may perhaps be attributed the generation of Calculi, and other diseases of the urinary system, as we shall have occasion to notice under the head of _Lithonthryptics_. The increased efficacy which these medicines derive from combination with each other, will form a subject of interesting enquiry in the succeeding essay. EXPECTORANTS.