Digitalis, a genus of exogenous plants belonging to the natural order scrophulariaceoe. Digitalis purpurea (Linn.), purple foxglove, is a small herb found wild in Europe about hedges on banks of streams, in a gravelly or sandy soil. Calyx 5-parted, unequal; corolla campanulate, the limbs obliquely 4-lobed; stamens 4; stigma simple; capsule ovate-acuminate; root of numerous long slender fibres, biennial; stem erect, 3 or 4 ft. high, commonly simple roundish with slight angles, downy; leaves dull green, alternate, ovate-lanceolate or elliptic-oblong, crenate, downy, rugged, and veiny, tapering at the base into winged footstalks, lower ones largest; raceme terminal, long, simple, of numerous large, pendulous, odorless flowers. Fuchs is regarded as the earliest botanist who mentions this plant, which he named digitalis (Germ. Fingerhut, thimble), on account of the blossoms resembling the finger of a glove. The term foxe-glove occurs in a MS. Glossarium AElfricoe, written before the Norman conquest, and in a MS. Saxon translation of Apuleius, both of which are among the Cotton MSS. in the British museum; but no Latin or Greek name was given to this plant previous to Fuchs in 1542. - This beautiful plant derives its chief interest from its medicinal properties, which reside in the leaves and seeds, the latter being small, roundish, and grayish brown.
Its active principle is digitaline, a yellowish bitter, uncrystalli-zable powder, neither acid nor alkaline, only sightly soluble in water and ether, but very soluble in alcohol. Unfortunately for medicolegal ends, it has no very well marked reactions, and in one case of criminal poisoning the evidence of its use consisted chiefly in the fact that a substance extracted from the stomach and ejecta of the person killed produced in animals, when given to them, symptoms resembling those produced by digitalis. The effect of digitalis has been tried on dogs, horses, rabbits, turkeys, domestic fowl, and frogs, and on all it has been found to act as a poison. The cerebro-spinal symptoms observed in animals are diminished muscular power, convulsive movements, tremors, and insensibility. When given in small doses to man, it is found to exercise a remarkable influence over the circulation, frequently reducing the pulse from 70 or 80 to 40 or 50 beats in the minute. According to recent views, the beats of the heart, although retarded by digitalis, are rendered more vigorous by it, and at the same time the smaller arteries are contracted, so that their tension is maintained, and in some diseases increased, in spite of the slow pulse.
The therapeutic effects of digitalis, including its diuretic action, depend almost wholly upon the improved tone of the heart and blood vessels which it brings about. Small doses of it in health generally, but not always, increase the water of the urine to a slight degree, the solids undergoing but little change. When poisonous doses are approximated, the force of the heart and tension of the arteries fall, and the pulse becomes first irregular, and afterward rapid. Nausea and vomiting are early toxic symptoms. It should be borne in mind that a toxic condition may be suddenly developed during the use of digitalis as a medicine, in consequence of its accumulation in the system. It3 undoubted beneficial effects in organic diseases of the heart can in most cases be best attained and preserved by keeping the dose strictly within the limits of what has just been described as the first stage of its action; that is, the stage in which the tension of the blood vessels is maintained. Digitalis is used chiefly in organic diseases of the heart, to fulfil indications suggested above. Its effect in dropsies, and possibly in some nervous affections, is secondary. The infusion, tincture, leaves in powder, and granules of digitaline are all used in medicine.
Its effects may also be obtained by the application to the abdominal surface of cloths steeped in an infusion of it. The dose of the infusion is about a table-spoonful; of the powdered leaves, a grain; of the tincture, 10 to 15 drops; of digitaline, 1/60 of a grain. Large quantities of digitalis are quite inert, either from too long keeping or from having been taken from immature plants. DIGITIGRADES, the tribe of the typical car-nivora, so called because they walk on the ends of the toes, as distinguished from the plantigrades, which, like the bear, place the whole foot upon the ground. This tribe includes the mustelidoe or weasels, the canidoe or dogs, and the felidoe or cats. All have the cheek teeth with cutting edges, the lower shutting within the upper, dividing the flesh of their prey like the blades of scissors. As their food would indicate, they have a simple stomach and a short intestine. Their carnivorous propensity may be measured by the tubercle or heel on the lower carnivorous tooth, and the number of false molars in front and of tuberculous teeth behind it; those having the simplest carnivorous teeth, and the fewest molars in front and behind, like the cats and the weasels, are the most sanguinary.
The characteristic marks in the skeleton are the long metacarpus and metatarsus, the elevation of the os calcis, and the shortness of the phalanges which alone rest upon the ground; and in the cats, the retractile claws. The extremities are formed for leaping and springing; from the pelvis as the fixed point, the three portions of the limbs are movable in alternately opposite directions; by the simultaneous flexion of these joints, and their sudden extension by powerful muscles, the greatest force is given to the spring, the elevated and elongated heel affording the principal mechanical advantage in the digitigrade foot.