This group includes as its most important members digitalis, strophanthus and squill. Others of the group are of minor importance. The drugs of the group increase the tone of the heart and arterial muscles and stimulate the vagus mechanism. In this way they slow and regulate the heart-beat, increase the cardiac output, and thus improve the circulation without affecting the blood-pressure directly. They are employed to secure compensation in valvular lesions, relieving the congestion, dyspnea, edema and other distressing symptoms and increasing the flow of urine. When administered by mouth, their absorption is slow and somewhat uncertain and their effects are correspondingly delayed and cumulative, so that they must be carefully watched. Overdoses produce nausea, vomiting, diarrhea, headache, cardiac irregularities and heart-block. The emetic action of ordinary doses is not due to local irritation, as commonly supposed, but is central and therefore cannot be avoided by rectal or intravenous administrations, or by the use of special preparations or isolated principles.