It is easy to imagine that any substance which is capable of entering the current of the circulation, and of stimulating the kidneys by a direct application to their secerning vessels, may occasion a more copious urinary discharge; in this manner the different saline[157] preparations, _Potass_, _Soda_, _Nitrate of Potass_, _&c._ are brought to the kidneys in the course of the circulation, and exciting the vessels to an increased action, promote the secretion of a larger proportion of watery fluid from the blood, in consequence of which, the absorbents are indirectly stimulated in order to supply the deficiency, and in this manner dropsical swellings are reduced. Water, as a simple diluent, will promote the action of the kidneys, and it is very judiciously remarked by Dr. Cullen, that by withholding the use of fluids in dropsy, you will diminish the quantity of fluids secreted, and allow the secretories of the kidneys to fall into a state of inactivity and collapse. This is a sufficient answer to those who defend the practice of enjoining an abstinence from all drinks in dropsy. b. _The diuretic remedy undergoing decomposition_ IN TRANSITU. The digestive organs appear to possess the power of readily decomposing all saline compounds into which _vegetable_ acids enter as ingredients, and of eliminating their alkaline base, which, being in the course of the circulation, carried to the kidneys, excites them into action, and promotes the excretion of urine; and it is probably in this way that the _Acetate_, _Citrate_, _Super-tartrate_, and other analogous combinations of _Potass_ and _Soda_ prove diuretic: on the other hand, it is equally evident that salts containing the _mineral_ acids are not under the control of the decomposing powers of the _chylo-poietic_ organs, and consequently do not undergo any changes _in transitu_, although some of these salts, as I have just stated, especially the more soluble ones, are absorbed entire, and prove diuretic. _Sulphate of Potass_, from its insolubility, is not readily absorbed, and its composition will not allow the developement of its base; we perceive therefore that it has not any tendency to produce an influence upon the urinary secretion.