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Show 132 RED PERUVIAN BARK TREE. There are two kinds of extracts madc, the hard andsoft. The chapter on Extracts and Resins in the London Pharma. copeeia is concluded with the two following general directions : 1. All the extracts, during the time of inspissation, must be gently agitated. 2. On all the softer watery extracts a small quantity of spirit of wine must be sprinkled. The Dublin college say,— All extracts, when they begin to get thick, ought to be frequently stirred with a clean iron spatula; and they may be reduced to a proper thickness by means of a stove, heated for that purpose. They must be kept as much as possible excluded from the action of the air; and the softer extracts are to be sprinkled with rectified spirit of wine. All these extracts are supposed to contain the virtues of the substances from which they are prepared, in a very pure and concentrated form; but this supposition is probably in several instances erroneous; and the directions for preparing them are frequently injudicious and unceconomical. As the changes which opium and aloes undergo bysolution and subsequent evaporation, have never beenascertained by careful and satisfactory experiments, well-selected pieces of these substances are to be preferred to the preparations in which they are supposed to be purified. As a further proof of the superiority of good opium over all its preparations, I mayalso remark, that the latter, however well prepared, soon become mouldy, the formernever. Cinchona bark is a medicine of very great importance; but, unfortunately, the proportion of woodyfibres, or inert matter, which enter into its composition is so great, that weak stomachs cannot bear it when given in quantity sufficient to produce any very powerful effects. On this account, the preparation of an extract, which way contain its active principles in a concentrated form, is a desirable object. On this subject thereis still much room for experiment. The London college, in its direc tions, certainly errs in two important particulars: in the first place, in desiring the decoction to be continued until the greatest part of the menstruumis evaporated ; and, in the secondplace, in separating, byfiltration, the powder which separates from the decoctionafter it has cooled. The first error probably originated in the old idea, that, by continuing theboiling fora great length RED PERUVIAN BARK TREE, L3S of time, more of the bark would bedissolved; but it is now understood that water is incapable of dissolving more than a certain quantity of the active principles of cinchona; and that, after the water has become saturated, by continuing the decoction we diminish the quantity of the menstruum, andtherefore also di- minish the quantity of bark dissolved. It is not easy to account for the second error; for, according to the old idea, that the powder which separated, on cooling, from a saturated decoction of cinchona, was a resinous substance, it surely ought not to have been rejected from what were supposed to be resinous ex- tracts. ‘This precipitate is now known to be caused by the much greater solubility of its active principles in boiling than in cold water, so that the precipitate is not different from what remains in solution. Accordingly, I have found by experiment that cinchona gave at least one half more extract when the decoction was conducted according to the directions of the Edin. burghcollege. The real advantage of so expensive an agent as alcohol in preparing any of these extracts, has not been demonstrated; and, if | be not misinformed, it is seldom employed bythe apo. thecaries in preparing even what are called the resinous extracts. Prescriptions, with Remarks. The best forms of prescription are: R.. t. Take of bark, in powder, ounce 14; Divide into twelve portions, of which take one in some milk every two hours in the interval of the ague fit; when this comes on take thirty drops of vitriolic ether and fifteen drops of laudanum in a decoction of liquorice, after which frequently take acupful of warm decoction of liquorice until the sweatingis over, when resume again the bark as before. R..2. Take of bark, in powder, - scruples 2, shake-root - °= ‘s# scruple 12 Make into a powder, to be taken every three hours in some porter. his is given in the advanced stage of putrid. fever ; some food of the farinaceous kind (not animal) is to be taken an hour after. Sometimes to the powder mixed with porter, a dessert-spoonful of yeast is added, producing a wonderful and unexpected result in cases the most forlorn. Rg 6 s K. 8. Take of bark, in powder - - - - ~ scruples? compound powderof chalk with opium, grains 10: |