In warm climates, the yellow fever is generally, as it was in Philadelphia in the month of August and in the beginning of September, 1793, a disease of but two or three paroxysms. It is sometimes, I believe, only a simple ephemera. In these cases, purging alone is sufficient to reduce the system, without the aid of bleeding. It was found to be so until the beginning of September, in 1793, in most cases in Philadelphia. The great prostration of the system in the yellow fever, in warm weather and in hot climates, renders the restoration of it to a healthy state of action more gradual, and of course more safe, by means of purging than bleeding. The latter remedy does harm, from the system being below the point of re-action, after the pressure of the blood is taken from it, or by restoring the blood-vessels too suddenly to preternatural action, without reducing them afterwards. Had bleeding been practised agreeably to the method described by Riverius (mentioned in the history of the fever of 1793), or had the fever in Jamaica run on to more than four or five paroxysms, it is probable the loss of blood would have been not only safe, but generally beneficial. I have, in the same history, given my reasons why _moderate_ bleeding in this, as well as many other diseases, does harm. In those cases where it has occurred in large quantities from natural hæmorrhages, it has always done service in the West-Indies. The inefficacy, and, in some cases, the evils, of _moderate_ blood-letting are not confined to the yellow fever. It is equally ineffectual, and, in some instances, equally hurtful, in apoplexy, internal dropsy of the brain, pleurisy, and pulmonary consumption. Where all the different states of the pulse which indicate the loss of blood are perfectly understood, and blood-letting conformed in _time_ and in _quantity_ to them, it never can do harm, in any disease. It is only when it is prescribed empirically, without the direction of just principles, that it has ever proved hurtful. Thus the fertilizing vapours of heaven, when they fall only in dew, or in profuse showers of rain, are either insufficient to promote vegetation, or altogether destructive to it.