The latest experiments, however, made on very large quantities of the bark, have shewn that Quina and Cinchonia exist simultaneously in all the three species; but the Cinchonia is, relatively to the Quina, in greater quantity in the grey bark; whilst, in the yellow bark, the Quina so predominates, that the presence of the Cinchonia might well have escaped notice when small quantities were operated on.
Having thus furnished a sketch of this curious discovery, we have next to enquire whether the alkaline bases in question do actually concentrate all the virtues of the barks in which they reside? M. Majendie[[466]] informs us that Pelletier had very early after the discovery transmitted to him a portion of the new substances for trial, and that he has unequivocally determined that they do not possess any deleterious qualities,[[467]] and are therefore essentially different from the principles of Nux vomica, (Strychnine,) Opium, (Morphia,) &c. According to the testimony of Dr. Double, as related in the same journal, they would seem to possess the medicinal properties of the cinchona.
In the third number of Majendie’s Journal we receive a report from M. le docteur Renauldin, of an intermittent cured by the Sulphate of Cinchonia, in doses of six grains.
As the discovery of an alkaline element in Opium led the way to the detection of salifiable bases in other active vegetables,[[468]] it has seemed to me preferable that I should introduce those general observations which I wish to offer upon the subject of those bodies, under the history of that narcotic. It is only necessary in this place to caution the practitioner against the hasty generalizations of the too sanguine chemist; it has already been observed that those vegetable remedies, whose value has been established by the sober experience of ages, consist of different principles of activity, or, at least, owe a modified power to the compound effect of their several ingredients. (p. 154, note.)
Solubility of the Bark.[[469]] Cold water extracts its bitter taste, with some share of its odour; when assisted by a moderate heat, the infusion is stronger, but becomes turbid as it cools; the infusion cannot be kept, even for a short time, without undergoing decomposition, and being spoiled; wine also extracts the virtues of bark, and is prevented by this substance from becoming sour, a fact which probably depends upon the avidity with which some of the principles of bark combine with oxygen, and which may throw some light upon the cause of its antiseptic virtues. The colouring matter of wine is precipitated by bark, as it is by charcoal, in the course of a few days. By decoction the active matter of cinchona is in a great degree extracted, but if the process be protracted beyond eight or ten minutes, it undergoes a very important chemical change, the precise nature of which is not well understood; the balance of affinities, however, by which the different elements are united, is evidently overthrown, and a considerable precipitation ensues; oxygen would also appear to have been absorbed; whether the Cinchonia becomes insoluble has not yet been ascertained, but experience has shewn that the general loss of solubility, produced by such a process, is accompanied with a corresponding loss of medicinal activity; on which account, the extract is necessarily a very inefficient preparation; if we attempt to redissolve it, not more than one half is soluble in water. Vinegar is a less powerful solvent than water; the active matter of bark is rendered more soluble by the addition of mineral acids, and by the earths and alkalies; these latter bodies deepen its colour, and precipitate the Cinchonia, for which reason, when they are employed, the decoction ought not to be filtered; see Form. 41, 42, and note thereon. Lime water has been recommended as a solvent, and it affords an excellent form for children and dyspeptic patients; for the same reason we obtain a stronger and perhaps a more efficient preparation, by triturating it with magnesia, previous to the process of infusion. Alcohol is a very powerful solvent, but the great activity of this menstruum so limits its dose that we are prevented from exhibiting a sufficient quantity of the bark in the form of tincture; it furnishes however an excellent adjunct to other preparations.
Incompatible Substances. Precipitates are produced by the salts of iron, sulphate of zinc, nitrate of silver, oxy-muriate of mercury, tartarized antimony, solutions of arsenic, &c. Any considerable portion of a tincture produces also a precipitation, which sometimes does not immediately take place, and the medicinal value of the bark is probably not impaired by it. As the infusions of nut galls and some other vegetable astringents precipitate the cinchonia from bark, it becomes a question how far such liquids are medicinally compatible; saline additions, as alum, muriate of ammonia, &c. have been frequently proposed, but in many such mixtures decompositions arise which must deceive us with regard to the expected effects. Forms of Exhibition. No form is so efficient as that of powder, a fact which would seem to argue against the exclusive value of the Cinchonia; even the ligneous fibre which the chemist pronounces to be inert and useless, may produce its share of benefit by modifying the solubility of the other ingredients, or by performing some mechanical duty which we are at present unable to understand or appreciate; but where the stomach rejects it, it must be administered in infusion or decoction, with the addition of its tincture. In cases where it is necessary to join cordials, an infusion of bark in Port wine[[470]] is a popular and very useful form for its administration. Dose of the powder, gr. v to ʒij or more, of the infusion or decoction ℥ij. Medicinal Uses. It is powerfully tonic and antiseptic; it was introduced into practice for curing intermittent fevers, but since that period it has been generally used in diseases of debility, in fevers of the typhoid type, and in gangrene. It was first conjectured to be useful in gout by Sydenham, and Dr. Haygarth has strongly recommended its exhibition in acute rheumatism; when however it is used in these diseases, the greatest attention ought to be paid to the state of the bowels, and purgatives should be occasionally interposed. In Dyspepsia, the use of the purer bitters is to be greatly preferred to that of the bark. Officinal Preparations. Infus. Cinchonæ, L.E.D. Decoct. Cinchon. L.E.D. Extractum Cinchon. L.E. Extract. Cinchonæ resinosum. L.D. Tinct. Cinchonæ, L.E.D. Tinct. Cinchonæ comp. L.E.D. Tinct. Cinchon. Ammoniat. L. Magistral Formulæ, 31, 37, 40, 44, 127. Adulterations. The frauds committed under this head are most extensive; it is not only mixed with inferior barks, but frequently with genuine bark, the active constituents of which have been entirely extracted by decoction with water. In selecting cinchona bark, the following precautions may be useful; it should be dense, heavy and dry, not musty, nor spoiled by moisture; a decoction made of it should have a reddish colour when warm; but when cold, it should become paler, and deposit a brownish red sediment. When the bark is of a dark colour between red and yellow, it is either of a bad species, or it has not been well preserved. Its taste should be bitter, with a slight acidity, but not nauseous, nor very astringent; when chewed, it should not appear in threads, nor of much length; the odour is not very strong, but when bark has been well cured, it is always perceptible, and the stronger it is, provided it be pleasant, the better may the bark be considered. In order to give bark the form of quill, the bark gatherers not unfrequently call in the aid of artificial heat, by which its virtues are deteriorated; the fraud is detected by the colour being much darker, and upon splitting the bark, by the inside exhibiting stripes of a whitish sickly hue. In the form of powder, cinchona is always found more or less adulterated. During a late official inspection of the shops of apothecaries and druggists, the Censors repeatedly met with powdered cinchona having a harsh metallic taste, quite foreign to that which characterizes good bark.[[471]] The best test of the goodness of bark is afforded by the quantity of Cinchonia, or Quina that may be extracted from it; and the manufacturer should always institute such a trial before he purchases any quantity, taking a certain number of pieces indiscriminately from the bulk. Much has been said of late concerning the probability of the genuine species of the cinchona tree becoming extinct; in consequence of which some succedaneum has been anxiously sought for; the bark of the broad-leaved willow, Salix Caprea, has been proposed for this purpose. Vogel recommends the root of Geum urbanum avens; others propose that of the Dastisca canabina.
The Cinchona Caribæa of the Edinburgh Pharmacopœia is said, by Dr. Wright, to whom we are indebted for our knowledge of it, to have satisfactorily answered in all cases where the Peruvian bark was indicated. The Geoffræa Intermis is often sold for it.
M. Ré, Professor of the Materia Medica at the Veterinary School at Turin, has announced that the Lycopus Europæus of Linnæus, called by the peasants of Piedmont the Herb China, is a complete succedaneum for Peruvian Bark.[[472]] The success with which bark has been imitated by medicinal combination, has already been noticed in the first part of this work.
CINNAMOMI CORTEX. L.E.D (Laurus Cinnamomum.)
Cinnamon.