_Jesuit’s Bark._
Notwithstanding the labours of the Spanish botanists, the history of
this important genus is still involved in considerable perplexity, and
owing to the mixture of the barks of several species,[459] and their
importation into Europe under one common name, it is extremely difficult
to reconcile the contradictory opinions which exist upon the subject,
nor indeed would such an investigation be consistent with the plan and
objects of this work. Under the trivial name _officinalis_, Linnæus
confounded no less than four distinct species of cinchona, and under the
same denomination the British Pharmacopœias, for a long period, placed
as varieties the three barks known in the shops; this error indeed is
still maintained in the Dublin Pharmacopœias, but the London and
Edinburgh colleges have at length adopted the arrangement of Mutis, a
celebrated botanist, who has resided in South America, and held the
official situation of Director of the exportation of bark for nearly
forty years.
CINCHONÆ CORDIFOLIÆ CORTEX. L.E. Cortex Peruvianus. D. Heart-leaved
Cinchona Bark, commonly called _Yellow_ Bark.
CINCHONÆ LANCIFOLIÆ CORTEX. L.E. Cortex Peruvianus. D. Lance-leaved
Cinchona Bark, common _Quilled_ bark—_Pale_ bark.
CINCHONÆ OBLONGIFOLIÆ CORTEX. L.E. Cortex Peruvianus. D. Oblong-leaved
Cinchona Bark, called _Red_ bark.
QUALITIES. The _odour_ and _taste_ of these three species are
essentially the same, although they differ in intensity. They are all
bitter, sub-astringent and aromatic, but the flavour of the _Yellow_
bark is incomparably the most bitter, although less austere and
astringent, whilst the red bark has a taste much less bitter, but more
austere and nauseous than either of the other species. CHEMICAL
COMPOSITION. Few vegetable substances have been more frequently, or more
ably submitted to chemical analysis than the Peruvian bark, and yet but
few results of any great practical utility had been obtained previous to
the recent experiments of Pelletier and Caventou, communicated to the
Academy of Sciences at Paris, since the publication of the fourth
edition of the present work.
Dr. Maton[460] had several years ago observed, that an infusion of
nutgalls produced a precipitate with the decoctions of Bark; a fact
which necessarily produced considerable speculation. Seguin was induced
to regard it as arising from the presence of _gelatine_, (_see p. 56_,)
an opinion which Dr. Duncan proved to be erroneous, and shewed that it
depended upon a new proximate principle, to which M. Gomez of Lisbon had
previously assigned the name of _Cinchonine_. Besides which, bark was
considered as containing resin, extractive, gluten, tannin, a small
portion of volatile oil, and some salts with a base of lime; one of
which however had been only found in _Yellow_ bark, and had been
discovered to contain a peculiar vegetable acid, denominated by
Vauquelin _Kinic_, a name which Dr. Duncan very judiciously superseded
by that of _Cinchonic_ acid.
In the _Red_ bark, Fourcroy detected also a portion of citric acid, some
muriate of ammonia, and muriate of lime. Upon which of these principles
the tonic and febrifuge virtues of bark depends, has ever proved a
fruitful source of controversy. Deschamps attributed them to _Cinchonate
of Lime_, and asserted that two doses of thirty-six grains each, would
cure any intermittent. Westering considered _Tannin_ as the active
constituent; while M. Seguin assigned all the virtues to the principle
which precipitates gallic acid, and which, as it has been before stated,
he mistook for gelatine. Fabroni concluded from his experiments, that
the febrifuge power of the bark did not belong exclusively and
essentially to the astringent, bitter, or to any other individual
principle, since the quantity of these would necessarily be increased by
long boiling, whereas the virtues of the bark are notoriously diminished
by protracted ebullition. This argument however will not go far, when we
consider the chemical changes which the liquid is known to suffer during
that operation, and by which a considerable portion of its matter is
rendered insoluble. Such was the state of our knowledge respecting the
composition of the _Cinchona_, when Pelletier and Caventou, guided by
analogy, were led to infer the presence of an alkaline element of
activity in its composition. The merit, belonging to the researches of
these eminent chemists, does not so much consist in the discovery of new
elements, as in the proofs which they have furnished of the well known
principle, _Cinchonine_, being a salifiable base,[461] and in
demonstrating the peculiar states of combination in which it exists in
the different species of Cinchona.