_Foxglove._
QUALITIES. The leaves, when properly dried, have a slight narcotic
_odour_, and a bitter nauseous _taste_, and when reduced to powder, a
beautiful green _colour_. CHEMICAL COMPOSITION. Extractive matter, and a
green resin, in both of which the narcotic properties reside; they
appear also to contain ammonia, and some other salts.[492] SOLUBILITY.
Both water and alcohol extract their virtues, but decoction injures
them. INCOMPATIBLE SUBSTANCES. See _Infusum Digitalis_. MEDICINAL USES.
It is directly sedative, although some maintain the contrary opinion,
diminishing the frequency of the pulse, and the general irritability of
the system, and increasing the action of the absorbents, and the
discharge by urine. The effects appear to be in a great degree connected
with its sensible influence upon the body, which is indicated by
feelings of slight nausea and languor; accordingly, every attempt to
prevent these unpleasant effects, or to _correct_ the operation of
digitalis, by combining it with aromatic, or stimulant medicines, seems
to be fatal to the diuretic powers of the remedy. Dr. Blackall, in his
“Observations upon the cure of Dropsies,” has offered some remarks which
bear upon this point, and to which I have before referred. _See page 96
& 150._
Several of the formulæ introduced under the class of diuretics are
combinations supported by high authority, but it is doubtful whether
their adoption can be sanctioned upon principle; they are however well
calculated to illustrate the nature of diuretic compounds, and this is
the only purpose for which they were selected. See _Form: 103_. The
French have introduced in their new Codex, an ethereal tincture,
_Tinctura Ætherea_ _Digitalis purpureæ_, in which the sedative influence
of the plant must be entirely overwhelmed by the stimulant properties of
the menstruum. Under the head of _Diuretics_, I have so fully considered
the value of diuretic combinations, and the _modus operandi_ of
Digitalis, that it is unnecessary to dwell upon the subject in this
place. Digitalis has considerable influence over the action of the
heart; and in certain diseases, attended with inordinate motions of that
organ, it proves eminently serviceable; I have employed it with great
satisfaction in cases of palpitation connected with a state of general
irritability, so frequently occurring in female disorders; and according
to my observations where it succeeds, opium generally does harm. _Form:
32._ FORMS OF EXHIBITION. In substance, tincture, or infusion; the
latter form is most efficient as a diuretic. DOSE of the powdered leaves
gr. j, in a pill, twice a day; the augmentation of the dose should
proceed at the rate of one-fourth of the original quantity, every second
day, until its operation becomes apparent, either on the kidneys, or on
the constitution generally. If it produce such a disturbance in the
primæ viæ as to occasion vomiting or purging, its diuretic powers will
be lost; in such a case the addition of a small portion of opium, or
opiate confection, may be expedient. The distressing effects of an
overdose are best counteracted by tincture of opium in brandy and water,
and by the application of a blister to the pit of the stomach. A London
Surgeon has lately stated that he has prescribed the tincture of
Digitalis, in the dose of twenty-five drops, three times a day, in
barley-water, with great success in Gonorrhæa. OFFICINAL PREPARATIONS.
_Infus: Digitalis_. L.E. _Tinct: Digital:_ L.E.D. _Decoct: Digitalis:_
D. It is very important that the leaves of this plant be properly
collected, and accurately preserved; they should be gathered when the
plant is beginning to flower, and, as it is biennial, in the second year
of its growth; the largest and deepest coloured flowers should be also
selected, for they are the most powerful; they should be also carefully
dried until they become crisp, or they will lose much of their virtue;
the too common method of tying them in bundles, and hanging them up to
dry, should be avoided, for a fermentation is produced by such means,
and the parts least exposed soon become rotten. The powdered leaves
ought to be preserved in opaque bottles, and kept from the action of
light as well as of air and moisture; a damp atmosphere has, upon a
principle already explained, a very injurious operation, by carrying off
those faint poisonous effluvia with which its efficacy seems to be
ultimately connected.