For persons, whose circumstances or duties retain them unavoidably in the midst of those suffering districts where the poison is most active, the best counsel I can offer--even if at first hearing it seem vague--is, that they should be vigilant as to preserving the greatest possible soundness and vigour of general health; keeping the body, so far as may be, undisturbed by extremes of heat and cold, undepressed by long confinement, unfluttered by violent passions, unexhausted by physical or mental fatigue, untried by any excess or any privation; taking for diet a sufficiency of fit and nutritive food, rather in generous measure than otherwise, but far from the confines of intemperance; and giving meanwhile a prompt attention and cure to whatever accidental ailments may arise. Such, in general language, are our best fortifications against the poison. It may be well, however, to add that in our metropolitan climate--perhaps everywhere else--the human frame tends to require some periodical aid from medicine. It may be the excitement and labour of London; it may be its atmosphere; it may be native peculiarity: but thus the fact stands--that there are few persons who do not at intervals require the re-establishing effects of what is called _tonic_ treatment. Probably three-fourths of the prescriptions we write are aimed at this mere tendency to depression in the human body, as manifested in one form or another. Now, as a man, going on some distant voyage of exploration, submits his chronometer to a last intelligent scrutiny, before he exposes it to the ordeal of other climates, so, in this matter of frequenting infected districts, men will do prudently, before they pass into perils which may test their powers of resistance, to see that they carry about with them no enfeeblement or disrepair which a short submission to medical discipline could effectually remove. For with epidemic poisons generally, and in a marked degree with Asiatic Cholera, it seems that all states of languor, depression, and debility enhance the risk of infection.[87] [87] For my medical readers, I may suggest that perhaps the daily use of _sulphate of quinine_, in small doses, during the height of the epidemic, would seem to deserve trial as a prophylactic; subject, of course, to what each practitioner is best able to estimate--of personal peculiarity in the patient, forbidding the use of this drug.--J. S., 1854. Beyond these general cautions, there is yet one which requires very particular mention.