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Show 136 minutes, with two drachms of bark and four ounces of pure water, in a similar mannerto the infusion with calcined magnesia, and, being filtered, was subjected to all the trials which were made with that infusion. Some little difference was perceived in favourof the infusion with calcined magnesia, but the other exhibited similar propertics in every respect. If, indeed, two infusions be prepared, the one with half a drachm of calcined, the other with the same quantity of common magnesia, the former will appear much stronger, the proportion of real magnesia being double; but when allowance is made for the presenceof fixed air in common magnesia, all the effects may be obtained fromit nearly, if not, in an equal. degree, with the calcined. Someexperiments were next instituted with magnesia and red bark, and conducted according to the method fully described in treating of the action of this earthy substance upon common Peruvian bark, but with a verydifferent result. It is remarkable, that in the trials with red bark no effects could be perceived either from common orcalcined magnesia. The colour of an infusion prepared in this way (3. e. by’rubbing two drachms of red bark and half a drachm of magnesia together, for fifteen minutes, with four ounces of water added in a gradual manner) is not deeper than aninfusion in simple water. If, however, the magnesia and red bark be kept infused a few hours after being well rubbed, the-liquor at length acquires a pretty deep red colour, but is not more bitter to the taste than the plain infusion of red bark in water. This difference in the action of magnesia upon the common and red bark, seems to point outa difference in the nature of their constituent parts*, which the other experiments were not capable of detecting. As all the substances which had acted upon quilled bark appeared to exert a more powerful action on the red, there was every reason to expect that the effects in the present instance should be similar. I confess myself rather at a loss for a satisfactory explanation of the difference, unless we suppose that the soluble parts of the red bark are already in such a state of activity as not to admit of any improvement from magnesia. mea * “> a » fe } r Phis %is a. valuable fact in order to detect the adulteration of this bark hy colouring ingredients sometimes practised. a RED PERUVIAN BARK TREE, RED PERUVIAN BARK TREE. 137 Many practitioners are in the habit of employing bark and lime water as a tonic in general:—Might not the calcined magnesia with bark be used as a substitute ? I have been long convinced, indeed, of the efficacy of the infusion with lime water, and am acquainted with several practitioners of experience who have frequently recourse to it with the best effects; and with regard to the preparation with magnesia, its sensible qualities are so highly in its favour, that Dr. Saunders has been induced to administer it frequently, both in the hospital and in private practice; and although very extensive trials would be necessary in order to form a decided conclusion, those which have been hitherto made have been far from proving unfavourable to this remedy. «¢ [ have,” ‘says Dr. Skeete, “* communicated my experiments and observations to several practitioners of my acquaintance, andafter a trial of the infusion, both in public and private business, I havereceivedas satisfactory accounts from them as the nature of the subject will permit.” In short, any person who will take the trouble of pres paring an infusion of bark with magnesia carefully, in the proportions and under the circumstances fully explained in the foregoing experiments, will soon be convinced, from its taste and appearance, that it must prove far moreefficacious than the common infusion. The rich red colour, its transparency for three or four days, and the length of time which it remains sound, without the addition of anyof the spirituous waters, are all qualities which should operate in obtaining it an extensive application to the purposes of medicine. It appears to me to be an excellent substitute for the decoctions and infusions of the red bark, and, if this be really the case, it is no small acquisiton. Notwithstanding the remarkable strength of the infusion with lime water, that with magnesia is preferable on several ac- counts; for, independent of its original superior strength, as far as experiments could direct us, it is less disagreeable to the taste, and keeps a much longer time without precipitation. We are not to stppose, however, that because the preparation of bark with lime water becomes turbid in a day or two, it loses much ofits strength. It does not appear at such a time to be in a State of fermentation, andstill retains its strong bitter taste. But besides employing magnesia in infusion with bark, I would propose that they should be given more frequently in sub- |