Digitalis. Digitalis. Foxglove. The dried leaf of Digitalis purpurea, or Purple Foxglove; the wild plant; Lin. Syst., Didynamia angiospermia. Indigenous.

Digitalinum. Digitaline. The active principle obtained from Digitalis. Description. The leaf is ovate, lanceolate, or oblong; crenate rugous, and downy, more especially on the under surface, which is veined; subsessile, or with a short petiole: of a dull green colour. The leaves should be gathered before the terminal flowers have expanded, the petiole and midrib removed, and the laminae carefully dried.

Prop. & Comp. Digitalis leaves have but little odour; their taste is somewhat bitter and acrid, they contain a non-nitrogenized amorphous principle, Digitaline, which occurs in white, or slightly yellow scales or mamillated masses; very bitter, without odour, but irritating to the nostrils; little soluble in water and ether, but readily soluble in spirit. Soluble in acid solutions, but without neutralizing them; its solution in hydrochloric acid soon becomes green: when burnt on platina foil it leaves no residue. Several other substances have been said to occur, to which peculiar names have been given, but whose nature and properties are but ill-understood. The leaves, however, contain some tannin.

Off. Prep. - Of Digitalis. Infusum Digitalis. Infusion of Digitalis. (Dried digitalis leaves, thirty grains; boiling distilled water, ten fluid ounces.) [Digitalis, in coarse powder, sixty grains; tincture of cinnamon, a fluid ounce; boiling water, half a pint. U. S.]

Tinctura Digitalis. Tincture of Digitalis. (Digitalis leaves, dried, two and a half ounces; proof spirit, twenty fluid ounces. Prepared by maceration and percolation.)

Digitaline is prepared by making a strong tincture of the leaves by digestion in rectified spirit at a temperature of 120°; and treating the extract obtained from the evaporation of the tincture with water acidulated with acetic acid; from this solution, after neutralization with ammonia, the digitaline is precipitated by tannic acid; the tannic acid is afterwards removed by rubbing the tannate of digitaline with oxide of lead (litharge), and spirit; by which an insoluble tannate of lead is formed, and the digitaline set free and dissolved by the spirit. This solution after decolor-ization with a small amount of animal charcoal is evaporated, and the residual digitaline washed repeatedly with ether to remove any impurities.

Therapeutics. When taken internally, the most marked effect produced by the drug is the weakening of the heart's power, accompanied by a diminished rate of the pulse; some observers assert, that the heart's action is primarily quickened. If the dose be increased, or continued after a certain amount of cardiac weakness has been induced, symptoms of an alarming character may arise, such as nausea, vomiting, faintness, and syncope: this is especially apt to occur when the patient attempts to make any exertion, or even to sit or stand up; in fact, patients under the full influence of the drug, which is sometimes purposely induced, are only in safety when in an horizontal position. Although digitalis acts so powerfully upon the heart, yet its influence over the capillary circulation, when in a morbid condition, is by no means so powerfully exercised as in the case of antimonial and mercurial preparations. Digitalis often produces copious diuresis, more especially when the deficiency of the urinary secretion depends on cardiac disease; it also occasionally induces sleep, or acts as a sedative and soporific, but only when the restlessness is due to an over-excited state of the heart. Digitalis is administered as a cardiac sedative in almost all cases where there is exalted action, whether sympathetic in nature, or depending on organic disease of that organ, or of the great vessels, as in hypertrophy, aneurism, or valvular disease, etc.; it should, however, always be borne in mind, that increased action of the heart is not always an indication of increased strength. Digitalis may be given also in haemorrhages of an active character, and as a diuretic in dropsies depending on the above-named cardiac diseases, and sometimes in other forms. Some practitioners have proposed the use of digitalis in inflammatory affections, but in these cases its efficacy has not been well established. It has also been employed in phthisis, but without permanent benefit; for although it often in these cases diminishes the rapidity of the pulse, it exerts no influence on the progress of the tubercular disease. Digitalis is generally asserted to be a drug the action of which is cumulative in character: the explanation of this peculiarity appears to the author to be as follows, viz.: that considerable weakening of the heart's action may occur without any very evident symptom being produced; but if this is increased above a certain point, so as to interfere with the efficiency of the circulation, then all the symptoms are rapidly and dangerously manifested.

Dose. Of the powdered leaves, 1/2 gr. to 2 gr.; of infusion, 2 fl. drms. to 1/2 fl. oz. or more; of tincture, 5 min. to 40 min. and upwards; of digitaline, 1/40 gr- to 1/10 gr.

Adulteration. Digitalis leaves are occasionally mixed with those of Verbascum thapsus and other plants. Attention to the characters of the true leaf, above given, will readily distinguish the admixture.