When the inflammatory action has proceeded unsubdued and has terminated in some change of structure, probably accompanied with copious effusion, as indicated by the symptoms detailed under the cases illustrating cerebral affection, advantage is sometimes obtained by affecting the system with mercury. In this condition of the brain it is not easy to bring the system under the influence of mercury; when it can be accomplished, the patient is commonly, though not invariably, snatched from death. In several instances I have known this treatment successful under apparently the most hopeless circumstances. When the success is most complete, the convalescence is invariably tardy, and often appears to be doubtful; the mind for a long time remains feeble, infirm, and almost fatuous; and, as in the two cases recorded by Pringle, though such patients recover of their fever, it is long before the nervous and the sensorial systems are restored to a sound state. The best mode of exhibiting mercury is in the form of a pill, consisting of two grains of calomel with half a grain of opium, given every three, four, or six hours. 3. To a fever which is severe from the commencement the preceding observations apply with double force. Then, if the most powerful remedies are not immediately employed, and if they are not brought to bear at once upon the severe symptoms in the completest combination, the case is wholly lost. The delay of an hour is pregnant with danger; the delay of a few hours places the efficacy of any measures that can be taken in great uncertainty; and the delay of a day or two renders their most vigorous application utterly useless. Whereas, knowing, as we now know, the condition of the organs upon which the severity of every case depends, and knowing remedies appropriate to that condition of sovereign efficacy, exceedingly few of such cases would be lost were these remedies employed with due vigour at the commencement of the attack. The typhoid symptoms with which it is commonly thought such cases commence would never appear. The patient would be convalescent, or at least would labour only under a mild form of fever at the period when, without these remedies, his condition would be hopeless. The practitioner ought never for a moment to forget that it is in the power of early and active treatment to deprive these severe cases of all their severity and, consequently, of all their danger; but that, after the lapse of a day or two, all human skill will be exerted in vain. It remains to say a word or two relative to the modification of the more powerful remedies, as the prominent affection may have its seat in the brain, the lungs, or the intestines. I. OF THE MODIFICATION OF THE TREATMENT IN CEREBRAL AFFECTION.