One of the most indisputable facts respecting the action of digitalis is the remarkable increase of blood-pressure which it occasions in the arteries. Of this fact, again, different explanations are possible. . Nearly all experimenters admit that digitalis produces contraction of the capillaries of the smaller arterioles, when taken into the general circulation;1 and this in itself would undoubtedly heighten the arterial pressure. But, on the other hand, the blood-pressure may be heightened by increased force of the cardiac contractions; and the observation of Meyer, that there is a continuous rise in the pressure up to a point almost immediately before death, when it suddenly falls to zero, has been made by Dybkowsky one of the chief arguments for the direct stimulation of the cardiac ganglia.

1 Handbook of Therapeutics, 3d ed., p. 390.

2 H. Fagge and Stevenson; Nunneley; Fothergill.

As for the contraction of the small arteries, this is believed by Traube and Bohm to depend on excitation of the vaso-motor centre in the medulla oblongata; but Ackermann discredits this idea, and holds that the contraction is due to direct action on the peripheral ends of the vaso-motor nerves, or even on the muscular coats of the arteries themselves.

The next point of importance is, whether digitalis is a necessary physiological provoker of diuresis, or whether the diuretic effects undoubtedly obtained in disease are due to the accidental morbid conditions which are present in the latter case. Over this question there hangs some doubt. The diuretic effects do not appear to have been very striking in any case, and in many instances severe digitalis-poisoning has been accompanied by partial suppression of urine.2 Ackermann states that digitalis acts diuretically only by increasing the fluidity of the blood, by facilitating the resorption of exudates, and suggests that by this means a part of the increase of blood-pressure may be caused.

Another interesting question concerns the cause of the reduction of temperature which is so marked and constant an effect of digitalis. This is probably due to an increased rapidity of circulation in the peripheral blood-vessels; for it must not be supposed that the slow pulsations of the heart indicate a diminished rapidity of the blood-current; on the contrary, their increased vigor causes the blood to circulate with abnormal swiftness: this causes increased transpiration, and a large loss of heat from the skin.

The more remote phenomena of digitalis-poisoning, especially those connected with the brain (giddiness, delirium, etc.), seem to be due entirely to changes in the circulation; there appears to be no direct action of the drug upon either brain or spinal cord.

Therapeutic Action. - When and by whom this now celebrated drug was first employed as a medicine is not known. The date of the earliest employment was certainly prior to 1597, since in that year a treatise on Foxglove was published by Gerarde. Parkinson shortly afterwards recommended it for external application in diseases of a scrofulous character; he also administered it internally "against the falling sickness." In. 1721 a place was given to it in the London Pharmacopoeia, but in the ensuing edition (1746) it was omitted. In the Pharmacopoeia of the Edinburgh College, digitalis has experienced corresponding alternations of repute and disfavor.

In approaching the subject of the therapeutics of so important a medicine, it may be well to observe, as a preliminary, that it is particularly adapted to persons of a sanguine or indolent temperament, with soft and lax muscles, and light hair. Dr. Withering long ago expressed his opinion that "digitalis seldom succeeds with men of great natural strength, of tense fibre, warm skin, and florid complexion, nor yet with people of tight and cordy pulse."

1 Nunnelly, however, denies this, except as a very limited secondary effect. 2 Christison on Poisons. Brunton on Digitalis.

The employment of digitalis in disease includes some of the most interesting and valuable applications of remedies that are to be found in the whole range of the medical art. The following are the principal points, though they do not exhaust the list of the uses of digitalis.

As a Tonic to the Heart, digitalis justly enjoys very high favor in a variety of morbid conditions. It is a singular fact that digitalis should have been regarded for so long a period solely as a cardiac sedative, seeing that its virtues as a stimulant tonic had been recognized by more than one old writer. The tide has now fully turned, and there is no better recognized fact in modern medical practice than the power of digitalis to sustain and strengthen cardiac action in a variety of morbid conditions.

To Traube we owe the credit of pointing out that the value of digitalis in correcting the disturbances in the circulation, caused by organic disease of the heart, is constantly referable to mechanical conditions; and that this is especially true in regard to the general venous byperaeinia which commonly accompanies such disease. The venous hyperaemia is dependent on general anaemia of the arteries, and originates when hypertrophy causes insufficient compensation, and when the heart is no longer competent to drive a sufficient supply of blood into the aorta. Two physiological effects of digitalis then become remedial - namely, the increase which the drug produces in the force and regularity of the heart's contractions, and the increase which it causes in the contractions of the smaller arteries. The action of digitalis is therefore most effective in cases of insufficiency of the mitral valves. In disease of the aortic orifice, compensation by hypertrophy continues to take place for so long a period that the use of digitalis may be dispensed with. Niemeyer1 remarks that "in digitalis we possess a very powerful means of moderating, not only hyperaemia of the lungs, but also engorgement of the aortic venous system which arises in mitral disease." "If we can succeed," he continues, "in retarding the action of the heart by means of digitalis, we afford time for the auricle to drive its contents into the ventricle through the contracted passage."