Having ascertained that digitalis does sometimes succeed in curing Phthisis Pulmonalis, it remains to discover what are the cases in which we may exhibit it with success. For this purpose it would be desirable to ascertain the _modus operandi_ of the medicine. Here writers have differed as widely as in their account of its success in practice. One author determines it to act by diminishing the force and frequency of the circulation, and reducing inflammatory action; a second attributes its salutary effect to its operation on the kidneys; while a third believes it no longer to be of advantage, when it increases the discharge by urine, excites nausea, vomiting, purging or any undue excitement, but attributes its beneficial effects to its stimulant efficiency, in invigorating the arterial and muscular energy of the system: and a fourth insists that by promoting the action of the absorbents it cures Consumption. These conflicting and opposite opinions constrain us to admit, that farther enquiry is necessary, before we can rest satisfied as to the mode in which digitalis acts. It must be confessed that this medicine is extremely uncertain in its operation. Its most evident effect, and that most insisted on, of reducing the frequency of the pulse, is by no means certain; and indeed, it is the opinion of Dr. Beddoes, that the force and strength of the pulse are increased by it. In the N. Y. Hospital I have witnessed frequent cases in which its continued exhibition produced no effect in reducing either the force or frequency of the pulse; and in some instances no effect at all seemed to be produced by it. A case occurred in that institution in October last, in which a patient, by his own carelessness took six drachms of Tinct: Digitalis with no evident injury. In examining the effect of this medicine on the pulse, it is necessary to recollect the remark of Beddoes, that it is very different in the recumbent and erect posture; the pulse frequently being found to be reduced in frequency and irregular in the former, but recovering its frequency and regularity in the latter situation. From the same author we learn, that if this remedy do not produce any good effect within three weeks, we can expect no advantage from it at all. It is generally admitted that digitalis will succeed only in the first stage of Phthisis Pulmonalis; in the last or ulcerated stage of that malady, it will not save our patient, but we are apprehensive, will rather hasten his dissolution. As it is acknowledged to be an uncertain medicine, we should not place our whole dependence upon it, nor suffer it to take the place of blood-letting and the rest of the antiphlogistic treatment before recommended: it should be used rather as an auxiliary than a principal remedy. From its uncertainty of operation it requires a cautious exhibition. The dose for an adult is from ten to fifteen drops of the saturated tincture, three times a day, and gradually increased until some effect is produced.