Rational practice can only be based on sound Pathology, and my object here is to give facts derived from bedside and post mortem observations. A very fatal epidemic of yellow fever prevailed in Gibraltar in 1828, from the middle of August until the 25th of December, a period of about four months and a half. The French government, desirous of collecting precise information respecting this disease, appointed a commission com¬ posed of MM. Louis, Trousseau, and Chervin, all gentlemen of the highest professional standing, for this important object. They proceeded to Gibral¬ tar, where they arrived on the 23d of November, only 33 days before the termination of the epidemic. The commission performed its duty ably and faithfully, and with the assistance of the eminent English and Spanish physicians, then in Gibraltar, viz.: Mr. Gillkrest, Fraser, Mery, Dias and others, collected a mass of most valuahle and interesting facts. It is a well-known law of epidemics, that they differ not only in their symptoms, but in their pathological characters in different years and places, and M. Louis, who has published a masterly analysis of the facts collected at Gibraltar, says : " I would beg the reader to remember that this work is not a treatise on yellow fever, but a history of the epidemic yellow fever which prevailed in Gibraltar, in 1828. .dll the general facts which result from my analysis may not befound in other epidemics." Now, although this work is put forth as the history of a small portion of one epidemic, many (overlooking the various grades and shapes which the same disease will assume at different epochs) have strangely received the facts and deductions of M. Louis as fixed and invariable laws. M. Louis has analyzed his limited and imperfect facts with all that ability No. XVIII.-April, 1845. * Since writine the above, I have received from France a Keport made to the Academy by M. Chervin.on a memoir ofM. Kufzon yellow fever.and I am gratified to see that my observations on the liver are here confirmed. M. Chervin states that lie has made five hundred autopsies after death from yellow fever, in the West Indies, Europe and Americti, and draws the following conclusions:-" 1st. That the lesion pointed out by M. I.ouis as constant in yellow fever, is often wanting, and that it is not rare to meet the liver in its normal condition in this disease. " 2d. That this organ shows not unfrequently a yellow colour in the remittent and intermittent fevers of hot climates, and that consequently the anatomical lesion, cited by M. Louis, is not characteristic of yellow fever, and that therefore the deductions which this physician has drawn from it fall of themselves." M. Chervin also shows that M.Rufz' dissections do not bear out M. Louis, although they have been quoted with this view.