1902 Encyclopedia > Digitalis (Foxglove)


DIGITALIS, or FOXGLOVE, a genus of biennial and perennial plants of the natural order Scrophulariacece. The common or purple foxglove, D. purpurea, is common oin dry hilly pastures and rocky places and by road sides in _various parts of Europe ; it ranges in Great Britain from Cornwall and Kent to Orkney, but it does not occur in Shetland or in some of the eastern counties of England. It flourishes best in siliceous soils, and is not found in the Jura and Swiss Aips. The characters of the plant are as follows :—stem erect, roundish, downy, leafy below, and from 18 inches to 6 feet or more in height; leaves alternate, crenate, rugose, ovate or elliptic-oblong, and of a dull green, with the under surface downy and paler than the upper ; radical leaves together with their petioles often a foot in length ; root of numerous, slender, whitish fibres; flowers lf-2£ inches long, pendulous, on one side of the stem, purplish crimson, and hairy and marked with eye-like spots within ; segments of calyx ovate, acute, cleft to the base ; corolla obtuse, with the upper lobe entire or obscurely divided ; stamens four and didynamous (see vol. iv. p. 138, fig. 226); anthers yellow and bilobed; capsule bivalved, ovate, and pointed ; and seeds numerous, small, oblong, pitted, and of a pale brown. As Parkinson remarks of the plant, " It flowreth seldome before July, and the seed is ripe in August;" but it may occasionally be found in blossom as late as September. In one variety, common in gardens, the flowers are white; in another their purple is of a coppery or metallic hue; and not unfrequently in cultivated plants several of the uppermost blossoms may be united together so as to form a cup-shaped compound flower, through the centre of which the upper part of the stem passes. A figure of D. purpurea will be found in vol. iv. plate xi. Many species of foxglove with variously-coloured flowers have been introduced into Britain from the Continent. The plants may be propagated by off-sets from the roots, but are best raised from seed.

The foxglove (Ang.-Sax., foxes-clife, foxes-glofa) is known by a great variety of popular names in Britain. In the south of Scotland it is called bloody fingers ; further north, dead-men's-bells ; and on the eastern borders, ladies' thimbles, wild mercury, and Scotch mercury. Among its Welsh synonyms are menyg-ellyllon (elves' gloves), menyg y llwynog (fox's gloves), bysedd cochion (red fingers), and bysedd y cwn (dog's fingers). In France its designations are gants de notre dame, and doigts de la Vierge. The German name fiugerhut (thimble) suggested to Fuchs, in 1542, the employment of the Latin adjective digitalis as a designation for the plant.

The leaves, gathered from wild plants when about two-thirds of their flowers are expanded, deprived usually of the petiole and the thicker part of the midrib, and dried, constitute the drug digitalis or digitalis folia of the pharmacopoeia. The prepared leaves have a faint odour and bitter taste ; to preserve their properties they must be kept excluded from light in stoppered bottles. They are occasionally adulterated with the leaves of Inula Conyza, Ploughman's Spikenard, which may be distinguished by their greater roughness, their less divided margins, and their odour when rubbed; also with the leaves of Symphytum officinale, Comfrey, and of Verbascum Thapsus, Great Mullein, which unlike those of the foxglove have woolly upper and under surfaces. The powder, infusion, and tinc-ture of digitalis are employed both externally and inter-nally ; and its active principle, digitalin, may further be used for subcutaneous injection. Digitalin, according to Nativelle, is a crystallizable, neutral, inodorous, bitter substance, of the formula C26H40O]6, insoluble in water and ether, but soluble in alcohol and chloroform. The earliest known descriptions of the foxglove are those given by Fuchs and Tragus about the middle of the 16th century, but its virtues were doubtless known to herbalists at a much remoter period. Gerarde, in his Herbal (1597), advocates the use of foxglove for a variety of complaints ; and John Parkinson, in the Theatrum Botanicum, or Theater of Plants (1640). tills us that

" The Italians have an usnall proverbe with them concerning this herb, called by them Aralda, which is Aralda tutte piaghe salda : Aralda salveth all sores It hath been found by late ex- perience to beavaileable forthe King's Evill .... also to be effectuall against the Falling Sicknesse, that divers have been cured thereby. "

Later, Salmon, in The New London Dispensatory, praises the remedy foxglove in no measured terms.

Digitalis was first brought prominently under the notice of the medical profession by Dr W. Withering, who, in his Account of the Foxglove (1785), gave details of upwards of 200 cases, chiefly dropsical, in which it was used. Having become acquainted with the drug in 1775 as an ingredient in a Shropshire family receipt for the cure of dropsy, he began to administer it as a diuretic, but at first in doses too large ; for, " misled by reasoning from the effect of the squills, which generally acts best upon the kidneys when it excites nausea," he sought to produce the same effect by foxglove. Further experience, however, convinced Mm " that its diuretic effects do not at all depend upon its exciting nausea or vomiting ; " and that often the urinary discharge may be checked when the dose is imprudently urged so as to occasion sickness. He moreover observed that in cases where the drug produced purging it was inefficacious unless combined with small doses of opium, so as to restrain its action on the bowels. Withering seldom found it to succeed in men of great natural strength, tense fibre, warm skin, and florid complexion, or in those with a tight and cordy pulse. He recommended digitalis _' in every species of dropsy, except the encysted:" and he was of opinion that it might be made subservient to the cure of diseases unconnected with dropsy, and that its power over the motion of the heart, to a degree unobserved by him in any other medicine, might be turned to good account by the physician.

The experiments of Marcet and Brunton show that the infusion of digitalis has a poisonous effect on various plants, and, even in very small quantity, kills fishes,—their auricles after death being found distended, their ventricles strongly contracted. On birds the effect of the infusion is to cause firm contraction of the left ventricle, and consequent excessive congestion of the lungs. A large turkey, according to M. Salerne (Hist, de l'Académie, 1748, p. 120, 12mo, and p. 84, 4to ed.), walked as if intoxicated, in consequence of partaking once of foxglove leaves. Another turkey, weighing 7 lb, ate during 4 days about half a handful of the leaves, after which it refused nourishment, and in a couple of weeks died, its weight being reduced to 3 lb. Handheld Jones and Fuller have proved that the infusion produces upon the hearts of frogs and mammals effects similar to those observed in birds. The usual results of small and repeated doses of digitalis are contraction of the capillaries, and augmented arterial blood-pressure, with slower and more powerful cardiac systole, and an increase in the urinary secretions ; large or long-continued doses, besides causing nausea or vomiting, often accompanied by purging, occasion a slow or irregular pulse, dilatation of the capillaries, decrease in the rate of respiration, cold sweats, disordered vision, chilliness of the extremities, giddi-ness, and great weakness, followed by convulsions and insensibility. Syncope is apt to occur on sudden changes of posture by patients fully under the influence of the drug. Its cumulative action, or unexpected production of alarmingly acute symptoms, may arise either from an increase in the dose, the elimination of the drug being constant, or from a check in the elimination, the dose remaining unaltered, hence the caution with which digitalis should be administered in cases where the renal functions are disturbed. The experiments of various physiologists have shown that digitalis, by stimulating the sympathetic ganglia of the heart, causes the contraction of 'its musculo-motor fibres, this effect being at first masked by a similar action on the pneumogastric nerves. By effecting more complete emptying of the ventricles in cases of cardiac disturbance, digitalis improves the circulation, bringing about in the lungs a more thorough oxidation of the blood. The consequent increased nutrition of the heart is promotive of hyper-trophy in that organ ; small doses of digitalis are therefore an assistance in hypertrophy following upon cardiac injury. In cases of dilatation of the heart, on the other hand, large doses are required. The continued use of the drug when the heart has become sufficiently hypertrophied may render ventricular action excessive. Digitalis calms excitement of the heart not by act-ing as a narcotic or sedative but by stimulating its nerves, and enabling it to contract without laboured effort. In feeble conditions of the circulation it acts diuretically by increasing arterial! tension, but its influence as a diuretic is not constant. Its efficacy in epilepsy appears to be limited by its action on the circula-tion. In enteric fever, erysipelas, and acute rheumatism, it has been employed to reduce temperature. Its use as a sedative in pneumonia, delirium tremens, and some other diseases has been objected to on the ground that it cuts off the irritating blood supply only by an extreme degree of ventricular contraction. In arachnitis in children, in inflammation tending towards serous effusion, in dropsy, haemorrhage, cerebral anaemia, and occasionally in angina pectoris and nervous palpitation, it is a valuable remedy. Upon the uterus digitalis acts by stimulating the ganglia in which its motor power resides (W. Howship Dickenson, in Med. Chir. Trans, vol. xxxix. Lond. 1865). In poisoning by digitalis, aconite and probably also Calabar bean may be resorted to.

A. L.J. Bayle, Bibliothèque de Thérapeutique, tom. iii. pp. 1-372; Christison, A Treatise on Poisons, p. 686, 4th ed. 1855; Sir H. Holland, Medical Notes and Reflections, chap. xxix. 3d éd., 1855 ; Trousseau et Pidoux, Traité de Therapeutique, vol. ii. p. 754, 1862 ; T. L. Brunton, On Digitalis, 1868 ; J. Milner Fothergill, Digitalis, its Mode of Action, and its Use, 1871; Pereira, Materia Medica, 1874; Garrod, Materia Medica, 1874; G. W. Balfour, Clinical Lectures on tlie Diseases of the Heart and Aorta, pp. 97 and 304, 1876. (F. H. B.)

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