P. E.—Leaves of second year's growth.
Properties: Cardiac tonic, indirectly diuretic.
Physiological action: In large doses digitalis is an irritant to mucous membrane, therefore will cause gastrointestinal disturbances, sneezing, nausea, increased action of the kidneys, sometimes even vomiting. In toxic doses the above symptoms are much more pronounced, there is purging, with green colored feces, violent vomiting, heart's action becomes irregular, vertigo, impaired vision, cold sweats, respiration becomes rapid and feeble, pulse irregular, great debility, coma, convulsions, and death follows from paralysis of the heart. It is a heart tonic and vascular stimulant. In small doses a heart stimulant, while in large doses it is a very powerful sedative. It gives the heart a rest by prolonging the diastole; thus permitting the vessels to become filled to their fullest capacity. In medium doses it slows the heart's action and increases its force. It stimulates the cardiac inhibitory apparatus, the cardiac motor ganglia and vaso-motor centers; thus contracting the arterioles and increases arterial tension. If too large doses are taken, or too frequent, it will result in overstimulation and finally paralysis; the heart's action being arrested in systole.
Use: As digitalis is a direct heart stimulant it is indicated in marked asthenic conditions; in prostration, surgical shock, in crisis of extremely exhausting diseases given with stimulants it generally acts promptly. It sustains the heart's action; but does not give tone to it, therefore it should be followed as soon as possible by other indicated agents. In asthenic fevers it will slow a rapid and feeble pulse; in prolonged fevers where temperature remains high and there is rapid, feeble and easily compressed pulse or irregular heart's action; all showing a failure of the vital forces, it is a valuable remedy. It will reduce the temperature, control pulse and improve the action of the heart. Here other sedatives may increase the trouble and are very often contra-indicated. On account of its cumulative action in the system and its irritating action on the digestive tract it should not be long continued and its effect carefully watched. Its cumulative effect often shows itself by decreased quantity of urine, and when this is noticed it should be discontinued. In emergency after taking large doses the recumbent position should be maintained. Its action is mainly on the inhibitory nerves and on the heart muscles. Although digitalis is used extensively the writer seldom uses it in his practice. We have less dangerous, less irritating and non-cumulative remedies, that give far better results in most cases. In many sthenic conditions where digitalis is used, lycopus virginica answers the purpose much better. However, as an emergency remedy, digitalis has its value.