This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Peruvian bark has been applied likewise, in conjunction with other appropriated medicines, and often with good success, to the cure of periodic head-achs, hysterical, hypochondriacal, vertiginous and epileptic complaints, and other disorders that have regular intermissions. By its bitterness, astringency, and mild aromatic warmth, it strengthens the whole system, and proves a medicine of great utility in weakness of the stomach, uterine fluxes, and sundry chronical diseases proceeding from a laxity and debility of the fibres. To strengthen the solids appears indeed, in all cases, to be its primary operation; and its salutary virtues in different diseases, to be no other than coniequential effects of this general power. In all the distempers where bark is known to take place, other astringent and bitter medicines, singly or combined, have likewise been of service, though not equally with this natural combination of them *(a).
The virtues of this bark are very difficultly extracted by long coction in water, and part of what the liquor is by heat enabled to take up begins to separate as Toon as it is cold. This resinous part, which is rather melted out by the boiling heat than dissolved by the water as a menstruum, seems to contain chiefly the astrin-gency of the drug: the bitter matter appears to be perfectly dissoluble, though more difficult to be got completely out. * After repeated in-fusion in cold water, till the liquor came off colourless and suffered no change from solution of vitriol, warm water extracted a considerable colour, and vitriol produced with this infusion an opake black: after warm water would extract no more, very hot water received a deeper colour than that of the strongest cold infusion of frcfh bark; and this likewise struck a deep black with vitriol: boiling water had the same effect, after very hot water had cealed to ad (a). On boiling a pound of finely powdered bark for an hour or two in five or fix quarts of water, the decoction whilst hot looks clear and reddish, but in cooling becomes turbid and of a pale yellowish or wheyish hue: in this state it is found to partake, in a great degree, both of the bitterness and astringency of the bark, but in proportion as it deposites the matter that made it turbid, it loses more and more of its stypticity, the bitterness seeming to continue undiminished. The remaining bark, boiled in fresh water, exhibits the same appearance for two or three times successively; and when, at length, it ceafes to render the water turbid, it imparts a bitterness without astringency, (b) retaining still some share fa) M. S. of Dr. Lewis.
*(a) Dr. Percival found, that on mixing insusion of bark with putrid or ox gall, an instant coagulation ensued, and the foqtor was increased. Hence he accounts for the disagreement of this medicine in the bilious fevers of the Weft Indies, Ess Med. and Exper. vol. ii. p. 24.
(b) In the above experiments, 1 judged of the astrin-gency only from the taste: solution of chalybeate vitriol, so useful on other occasions for discovering aftringcnt matter share of bitterness itself. The vapour which exhales in the first coction being caught in proper vessels, condenses into a limpid liquor which smells strrongly of the bark; though no separable oil is obtained on submitting many pounds to the operation. The several decoctions, (trained and infpifTated together, yield an extract, rather less bitter, and much less styptic, than the bark in substance: this extract is kept in the shops in a soft and a hard form; the one of a proper consistence for making into pills; the other fit for being reduced into powder.
As in vegetable decoctions or infusions, seemed here to fail; for having often mixed it, in different quantities, with even the first decoctions of bark, it produced, not a black, but a deep green. I have since observed, that when the vitriolic solution is used in very small proportion, it strikes a black with the turbid decoctions of bark, as with other astringents; and that even the green mixtures, resulting from a greater addition of the vitriol, on being largely diluted with water, become black or bluish like diluted ink. The resinous matter, which subsides on Handing from the turbid decoctions, being dissolved in spirit of wine, gave likewise a black with vitriol. But when the bark had been boiled in fresh waters, till it no longer gave any turbidnefs to the liquor, the last transparent decoctions, though still pretty strong in taste, gave no blackness at all.
Some doubts having arisen with regard to this experiment, I have repeated it twice, and found the event both times the same as before. The last decoctions, on dropping in the chalybeate solution, contracted indeed a slight dusky hue, which in certain positions might be mistaken for a low degree of blackness; but the mixtures, held between the eye and the light, appeared only of a kind of olive yellowish or brownish colour, and, on standing for a little while, de-posited, not a black, but an ochery precipitate; whereas the first infusions or decoctions, though so far diluted with water as scarcely to discover any taste, struck a bluish colour like that of diluted ink, and what little precipitate could be separated was black.
After the boiling of the bark in water had been repeated till the filtered liquor no longer made any change with folution peruv. molle & durum Ph.
Extr. cort. Lond.
As this drug gives out its virtue so difficultly and imperfectly to boiling water, it has not been suspected that cold water would have any considerable action on it: I have nevertheless found, that an infusion in cold water, though perfectly transparent, is rather stronger in taste than even the turbid decoction, though the latter has somewhat more of a kind of fulness in the mouth (a). It is by means of a gummy matter tion of vitriol, the remaining bark gave no tincture at all to rectified spirit.
But fresh bark, boiled in fucceffrve portions of rectified spirit, till it ceased to impart any colour to the menstruum, gave still a deep tincture to boiling water; and this decoction, on the addition of solution of vitriol, exhibited nearly the same appearances as the last decoctions above-mentioned, only in a higher degree, the precipitate being much more copious, and its colour deeper.