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Show 124 COMMON PERUVIAN BARK TREE. form of a dry powder, it must either be diffused in some liquid, as water, wine, or milk, or mixed with someviscid substance, as currant jelly. Its taste, which is disagreeable to many people, is best avoided by taking it immediately after it is mixed with the vehicle. In this respect, therefore, it is better for the pa< tients to mix it up themselves, than to receive it from the apo. thecary already made up, into a draught with some simple distilled water, or into an electuary with a syrup. A much more important objection to giving cinchona in substance is, that some stomachs will not bear it, from the oppression, and even vomiting, which in these cases it excites. We must endeavour to obviate this inconvenience by the addition of some aromatic, and by giving it m small doses more frequently repeated. Lf we are unable to succeed by these means, we must extract the most active constituents of the bark by means of some menstruam. It has therefore long been a pharmaceutical problem to discover which menstruum extracts the virtues of cinchona most completely. But it would be contrary to analogy to suppose that its coustituent principles should subsist so intimately mixed as they must be iman organic product, without exerting upon each other some degree of chemical affinity, and forming combinations possessed of new properties. Accordingly we find, whetherit arise from this cause, or merely from the state of aggregation, that neither water nor alcohol extracts these constituents from cinchona bark in the same quantity in which they are able to dissolve them separately, and that we must have recourse to direct experiment to determine the degree of action possessed by each menstruum upon it. With this view, many experiments have been made, and by very able chemists. But most of them were performed when thescience of chemistry was but inits infancy ; and even at this time that branch of it whichrelates to these substances is so little understood, that the results of the Jatest experiments are far from conclusive. 2. In infusion. To those whose stomachs will not bear the powder, this is the best form ofexhibiting cinchona bark. Water, ata given temperature, seems capableof dissolving only a certain quantity of its active constituents, and therefore we are not able to increase he “on eth inf. tO ‘ther : ia a the 1 strength of San an infuston, either by 7employing a larger qaantity of the bark, or allowing them to remain longer in contact. One COMMON PERUVIAN BARK TREE, 125 part of bark is sufficient to saturate sixteen of water in the course of an hour or two. ‘To accelerate the action of the water, it is usual to pourif boiling hot upon the bark, to cover it up, and allow it to cool slowly. After standing a sufficient length of time, the infusion is decanted off for use. The propriety ofthis process may, however, be doubted; for if a cold infusion be boiled, or even gently heated, it acquires a deeper colour, and lets fall a resinous matter, in part insoluble in alcohol and in water. The infusion in water is, however, liable to one very great objection, that it cannot be kept even a very short time without being decomposed and spoiled. Therefore, in some ine stances we prepare the infusion with wine; and it fortunately happens that very often the use of the menstruum is as much indicated as that of the solvent. Cinchona also prevents wine from becoming acid, but in the course of a few days throws downits colouring matter, as nut-galls and charcoal do. 3. Intincture. The great activity of the menstruum in this preparation prevents the bark from being given in sufficiently large doses to exert its peculiar virtues. It is, however, a powerful stimulant. 4, In decoction. Water of the temperature of 212° is capable of dissolving a much larger proportion of the soluble parts of cinchona bark than water at 60°, But the solvent powers evenof boiling water have their limits, and by protracting the decoction we do not increaseits strength, but rather, by diminishing the quantity of the menstruum, we lessen the quantity of matter dissolved. Be- sides, at a boiling temperature some of the active constituents are dissipated, while others absorb oxygen rapidly from the at. mosphere, and are converted into what seems to be an insoluble and inert resinous substance. 5. In extract. In this preparation we expect to possess the virtues of cin- chona bark in a very concentrated state. The principal objections to its use areits great expense, andthe decomposition and destruction of the active constituents of the bark during the preparation, even when most carefully conducted. Not above half the weight of the dry extract is again soluble in water. It is ‘onvenient for the formation ofpills and boluses, but we would |