(Fox-glove.)

Origin.- The dried leaves of Digitalis purpurea L., collected from plants of the second year's growth at the commencement of flowering. The plant is a biennial, 2 to 5 feet (0.6-1.5 M.) high, indigenous in Southern and Central Europe, and growing wild as far north as Norway. It is also found in Madeira and the Azores, and is well known everywhere as an ornamental garden plant.

Description and Properties. - From 4 to 12 inches (10-30 Cm.) long, ovate or ovate-oblong, narrowed, with a petiole, crenate, dull green, densely and finely pubescent, wrinkled above, paler and reticulate beneath, midrib broad near the base; odor slight, somewhat tea-like; taste bitter, nauseous. The leaves of mullein, Inula coryza and Inula Helenium, are sometimes mixed with those of fox-glove.

The study of the active principles is fraught with much difficulty, and at the present time it is by no means certain what all of the active bodies are. The following are among the most important constituents: Digitalin, C35H66O14, a crystalline glycosidal substance, insoluble in water. Digitalin is found mostly in the seeds. Digitonin, C27H48O14, is another constituent found in greater abundance in the seed, but also present in the leaves. It is a white, powder-like glycoside resembling saponin. It is soluble in water and insoluble in alcohol. A watery solution is capable of holding the water-insoluble glucosides in solution or in suspension. It is an active diuretic principle; digitoxin, C35H54O11, is the chief glycoside of the leaves and the most active constituent of the plant. It is insoluble in water, soluble in alcohol, chloroform, and ether; digitophyllin, C32H62O10, is another glycoside derived from the leaves. It resembles digitoxin. Digitalein and digitin are also present, but are of less importance.

Dose. - 1/2-2 grains (0.03-0.12 Gm.) [1 grain (0.065 Gm.), U. S. P.].

Official Preparations

Extractum Digitalis - Extracti Digitalis - Extract of Digitalis. - Dose, 1/6-1/2 grain (0.01-0.03 Gm.) [1/5 grain (0.01 Gm.), U. S. P.].

Fluidextractum Digitalis - Fluidextracti Digitalis - Fluidextract of Digitalis.Dose, 1/2-2 minims (0.03-0.12 Cc.) [1 minim (0.05 Cc), U. S. P.].

Infusum Digitalis - Infusi Digitalis - Infusion of Digitalis (1 1/2 per cent.). Dose, 1-4 fluidrams (3.7-15 Cc.) [2 drams (8 Cc.), U. S. P.].

Tinctura Digitalis - Tincturae Digitalis - Tincture of Digitalis (10 per cent.). - Dose, 5-20 minims (0.3-1.2 Cc.) [15 minims (1 Cc), U. S. P.J.

Unofficial Preparations

Digitalinum - Digitalini - Digitalin. - Description and Properties. - An amorphous, yellowish-white, crystalline powder or scales, or light, white crystalline tufts of needles, odorless and of an intensely bitter taste. Insoluble in water, soluble in alcohol. - Dose, 1/100-1/30 grain (0.0006-0.002 Gm.).

Digitoxin - Digitoxin - Digitoxin. - Description and Properties. - A white crystalline body, of a bitter taste; insoluble in water, soluble in chloroform. - Dose, 1/200 - 1/100 grain (0.0003-0.0006 Gm.).

Antagonists and Incompatibles. - The most complete antagonist is saponine, the active constituent of Saponaria officinalis. The cardiac depressants antagonize the action of digitalis upon the heart, morphine and the emetics possessing a similar property, though in less degree.

The incompatibles are the ferric chloride and sulphate, preparations of cinchona, tannic acid, and preparations containing it, and the subacetate and acetate of lead.

Synergists. - The cardiac action of digitalis is aided by other members of this group, and also by belladonna and ergot.

Physiological Action.- Externally and Locally. - Digitalis is at first irritant to the skin and mucous membrane. Later it may paralyze the sensory end-organs and thus prove an analgesic. Digitoxin seems to be the most active constituent in causing the irritant action.

Internally. - Digestive System. - Small doses ordinarily produce no effect upon the stomach. Large doses act as a gastro-intestinal irritant, exciting nausea, vomiting, and diarrhea. These effects may follow the prolonged administration even of small doses.

Circulatory System. - The principal effects of digitalis are upon the circulatory apparatus, the action of the drug varying according to the size of the dose.

In discussing the action of digitalis on the circulatory apparatus, both the results on the heart and on the blood-vessels need considering. So far as the heart is concerned two important factors should be borne in mind: the heart-muscle itself, and the cardiac regulating apparatus, particularly the vagus inhibitory action. Digitalis, as well as all the members of the series, exerts a markedly irritant action on heart-muscle; it also acts, as has been pointed out, as a distinct primary irritant and stimulant to the medulla, hence on the vagus nucleus. There is a play between these two factors, and the effects of digitalis on the heart are to be interpreted in accordance with the respective influences of these two conditions.

Very small doses of digitalis show practically only the results of mild muscle-stimulation. They cause, particularly in susceptible individuals, a slight increase in the force and rapidity of the heart-action.

Larger doses, and especially when repeated, bring out the so-called "therapeutic action" of digitalis. As the heart-muscle feels the stimulation before the vagus center is affected, there is usually, under medicinal doses, a preliminary increase in the rapidity of the heart's action, as well as a distinct increase in its force. In from three-quarters to one hour after giving a medicinal dose the second factor, inhibition, from vagus stimulation, becomes apparent; in some cases it may take several hours fully to establish the vagus action; then the heart-rhythm becomes slower, the force is increased, the systole is more complete and effective, and usually a larger amount of blood is being pumped every hour throughout the body, and also into the body of the heart-muscle itself.