Digitalis Purpurea. Foxglove.
Nat. Ord. — Scrophulariaceae. Sex. Syst. — Didynamia Angiospermia.
Description. — Foxglove is an elegant plant with a biennial, whitish, fibrous root, which in the first year sends up large tufted leaves, and in the following summer, a single, erect, wand-like, roundish with several slight angles, downy and leafy stem, rising from two to five feet in hight, and terminating in a spike of purple flowers ; the lower leaves are ovate, acuminate, rugose, crenate, downy, especially on their under surface, veined, of a dull -green color above and paler beneath, tapering at the base into short, winged petioles, about eight inches in length and three in breadth, and spreading on the ground ; the upper or cauline ones are alternate, elliptic-oblong, somewhat decurrent, and in other respects like the former. The flowers are very numerous, large, pendulous, scentless, on short peduncles, and are arranged in a long, erect, one-sided, terminal spike. At the base of each peduncle is a sessile, ovate, and acuminate floral leaf. The calyx is divided into five segments, rounded or acute, much shorter than the corolla, of which the uppermost is the narrowest. The corolla is monopetalous, campanulate, spotted within as well as hairy, inflated on the lower side, and narrowed at base, the upper lip somewhat cleft, emarginate, and smaller than the lower. The stamens are didynamous, subulate, inserted into the base of the corolla, declined, white, supporting large, oval, acute, deeply-cleft, naked anthers. The ovary is pointed, ovate, having a simple style, with a bifid stigma. The capsule is ovate, acuminate, two-celled, two-valved, with a septicidal dehiscence, and containing numerous small, oblong, pale-brown, pitted seeds.
History. — Foxglove is a native of the temperate parts of Europe, where it grows wild, and is cultivated in this country ; it flowers in June and July. The leaves and the seeds are active, though the former are the officinal parts. The full grown and perfectly fresh leaves are gathered in the second year about the period of inflorescence, the petioles and midrib being rejected, and are then dried by exposure to a current of dry air, by being placed in a drying-stove, or by being inclosed in a hot-air press. Much care is necessary in preserving them for medical purposes, or else they will prove inefficient. When well prepared, the powder has a fine green color, and retains the intense bitterness of the fresh leaves. The dried leaves or the powder should constantly be kept in well-closed, opake vessels, so as to exclude light and moisture. Age deteriorates its virtues, consequently the drug should be renewed yearly. The compact masses of digitalis prepared by the Shakers, are seldom of good quality, being much disposed to moldiness ; but when free from this they may be used with advantage, if recently prepared. We consider this, however, a very objectionable mode of preserving this, as well as many other, agents. In the fresh state, foxglove has but little smell, but when dried emits a faint, narcotic odor ; the fresh juice has a faint, mawkish smell, and is easily evaporated spontaneously without undergoing decomposition, forming a firm, elegant extract. The taste of the leaves and juice is intensely bitter, nauseous, and permanent. The dried leaf is of a dull, pale-green color, with a whitish down on its under surface ; the powder is of a fine deep green. Water, alcohol, ether, or diluted acids take up its virtues. A solution of sesquichloride of iron added to infusion of digitalis, renders it darkgreenish-black — tincture of galls causes a gray precipitate ; when triturated with lime, the leaves give out ammonia. Digitalis contains a volatile oil, a fatty matter, a red coloring substance similar to extractive, chlorophylle, albumen, starch, sugar, gum, lignin, salts of potassa, and lime, digitalic acid, volatile antirrhinic acid, and a neutral, energetic principle, upon which its properties chiefly depend, called digitalin. Dr. Morries obtained a narcotic empyreumatic oil by the destructive distillation of the leaves.
Digitalin may be prepared as follows : — First, prepare an alcoholic extract, by making a paste of the coarsely powdered leaves with rectified spirit, expressing the solution, and distilling off the spirit — this extract is to be treated with distilled water acidulated with acetic acid, and heated to about 110° F., a little animal charcoal being added. To the liquor, filtered, and partially neutralized by ammonia, a fresh concentrated infusion of galls is gradually added, so long as a precipitate is produced. This precipitate, which is tannate of digitalin, is obtained separate by decanting the liquid, washing it with pure water mixed with a little alcohol, and then rubbing it in a mortar, with one-third of its weight of very finely-powdered litharge. The mixture is gently heated, and submitted to the action of twice its volume of alcohol at about 90°. The alcoholic solution is treated with a little animal charcoal, filtered, and evaporated at a very gentle heat. The residue is acted on twice or three times with cold sulphuric ether, which removes impurities and leaves the digitalin. This may be powdered, or obtained in small scales by dissolving it in the least quantity of alcohol, and allowing the concentrated solution to evaporate in a stove upon plates of glass. One hundred parts of the leaves yield about one part of digitalin. It is white, inodorous, crystallizing with difficulty, intensely bitter, sternutatory when powdered, slightly decomposed at a boiling heat, soluble in about two thousand parts of cold water, more soluble in boiling water, which retains one part in one thousand when it cools, very soluble in alcohol, slightly soluble in ether, incapable of precipitating salts, neutral, and devoid of nitrogen. It prevents fermentation in an aqueous solution of sugar, and is probably a poison to beer-yeast. With tannic acid it forms an insoluble compound ; to concentrated muriatic acid it imparts a fine emerald-green color. The seeds are preferable to the leaves, as they contain a larger amount of digitalin, and can be better relied upon as to time of collection, preserving, etc.
Properties and Uses. — In single large doses, digitalis is an irritant narcotic poison, producing, nausea, vomiting, stupor or delirium, purging, cold sweats, extreme prostration of strength, a slow, feeble, irregular pulse, hiccough, suppression of urine, coma, convulsions, and death. In doses sufficient to bring the system under its immediate influence, it causes an augmented and permanent flow of urine, reduces the pulse to forty or even thirty beats in a minute, with languor, nausea, occasionally anxiety and salivation, a sense of weight or constriction and dull pain in the head, giddiness, dimness of vision, and more or less confusion of the mental faculties; occasionally it gives rise to irritation of the pharynx, larynx, trachea and esophagus, with hoarseness. And if the use of the remedy be persisted in, these effects will continue to increase, until the poisonous symptoms, first referred to, become developed. In medicinal doses, foxglove is sedative and diuretic, and may be employed with advantage in febrile diseases, acute inflammations, neuralgia attended with irritative fever, hemoptysis, palpitation of the heart, mania, epilepsy, pertussis, and spasmodic asthma. As a diuretic, in dropsy connected with diseased heart or kidneys. It should always be used with care, as it will sometimes act suddenly with an accumulated influence, and endanger the life of the patient. When its effects begin to appear, its use should be suspended for a time, as it is very permanent in its action, and if its sedative effect is too great, it is best counteracted by the use of wine and opium conjointly. Dose of the powder from one to three grains ; of the tincture from ten to twenty minims, either being repeated two or three times daily, and gradually increased until some effect is produced upon the head, stomach, pulse, or kidneys, when it should be diminished, or entirely omitted.
The poisonous effects of digitalis are best counteracted by first evacuating the stomach by the free use of warm liquids, if any of it is supposed to remain in the stomach, and then administering brandy, wine, ammonia, or other stimulants, with sinapisms to the wrists and ankles.
Digitalin produces similar effects on the system with digitalis, but its internal employment is hazardous, and requires great caution. If given at all, it should be commenced with the fiftieth of a grain, and gradually and cautiously increased to an amount not to exceed the twelfth of a grain.
Off. Prep. — Tinctura Digitalis.