If, then, the above view of the therapeutical action of mercurials be correct, it is easy to understand how, in cases of jaundice from permanent {106} obstruction of the gall-duct, the administration of mercury or any other lowering medicine, must prove detrimental by hastening the fatal termination. Although mercury has not, there are some substances which have, the power of exciting the flow of bile, just as there are substances which excite the flow of saliva. Among these the mineral acids, and soluble alkalies, hold the first rank. It may seem strange that acids, and alkalies, should be here placed in juxta-position; but the reason of this arrangement will immediately appear. According to a physiological law, acid substances have the power of exciting alkaline secretions, and alkaline substances of stimulating acid secretions. Bile being an alkaline secretion, we can therefore have no difficulty in understanding how the mineral acids act in cases of jaundice from suppression, induced, for example, by enervation. They simply stimulate the secretion of bile. It is not so easy, however, to comprehend the action of alkalies in similar cases. My explanation of their action is as follows:--When taken after food, and when taken on an empty stomach, the action of an alkali is entirely different. After food, and during digestion, the stomach contains a {107} quantity of acid gastric juice, and an alkali taken then, only neutralizes the acid. On the other hand, when an alkaline substance is introduced into an empty stomach, it acts according to the general law of exciting an acid secretion; consequently, an immediate flow of gastric juice takes place. And I believe it is the excess of this acid gastric juice, which, on reaching the duodenum, stimulates the secretion, and excites the flow from the gall-bladder of the alkaline bile, just as the mineral acids do under similar circumstances. One remark further is, however, necessary. The quantity of alkali employed for the purpose of stimulating the secretion, or of exciting the flow of the already secreted bile must be small, for if much be used, the greater part of the gastric juice will be rendered useless, in consequence of its being neutralized as fast as it is secreted. It may be laid down as a general rule, that when we desire to increase the flow of bile by means of a mineral acid, the acid must be given _after food_. When, on the other hand, an alkali is selected for that purpose, the alkali must be administered _before food_. For obvious reasons, both alkalies and acids are counter-indicated in cases of jaundice resulting from active congestion of the liver; and it is equally evident that they can be of no direct {108} service in jaundice arising from occlusion of the bile-duct, where our object would be rather to diminish than to increase the secretion of bile.