The Peruvian bark is, in many cases, one of the most useful internal remedies. It was originally introduced into medicine, about one hundred and fifty years ago, as a cure for intermittent fever; and its utility in gangrene is said to have been discovered by its curing this disease in a person who had it combined with ague, and who was taking the bark on account of the latter complaint. For many years after it was known in Europe, great prejudices prevailed amongst physicians against its use, partly on account of its having been improperly administered, but still more because it was so unfortunate as to cure diseases without necessarily either sweating or purging the patient, a fact which could be only ill explained, or rather scarcely allowed to be possible, by the prevailing theories of physic. Accordingly, although the cases in which it had been successful were by no means a secret, and although severals had the courage to employ it, in spite of all speculative arguments, yet neither Dr. Boerrhave, nor his commentator, Van Swieten, thought it expedient either to recommend or prescribe it. Renewing the motion of the stagnating blood by venesection, and the exhibition of trifling remedies, which could scarcely be called cordial, although sometimes dignified with that epithet, together with the external application of ardent spirits, or oil of turpentine, constituted the current practice in gangrene. These prejudices against the bark, which originated in ignorance, and were supported by attention to a foolish theory, continued long; but the want of a better remedy began at last to make them gradually give way, and the success of empyrics who used the bark soon completed their downfal. The bark induces an action nearly similar to the natural one, which is greatly injured, and, therefore, it gives a check to the progress of the disease; but, if its operation be not assisted by nourishment, &c. its good effects soon subside, because the materials whence new energy can be drawn are withheld, and, therefore, the system cannot profit so much by the establishment of the new action, and by the restoration of the power of converting the vital principle of foreign matter into nervous energy. The bark, then, is of service in two points of view: First, it changes directly the action of the system, it induces, in a considerable degree, an action somewhat similar to the natural action, and, therefore, counteracts the general action of descent which was taking place. Secondly, by inducing this action, it, to a certain degree, produces the same effects for a time which would have been produced by the natural action itself, or increases the power of renewing vitality; for, in the preliminary dissertation, it was mentioned, that the production of energy was exactly proportioned to the perfection and healthiness of the existing action. The good effects of bark, then, cannot be obtained without nourishment and free air.