ABSTRACT
The history of cities besieged for a considerable time, in which scarcity had been gradually increased to famine, would furnish many instances to illustrate the point. In a diary, which was kept of the celebrated siege of Londonderry, where the inhabitants were compelled to eat unwholesome provisions, dysentery prevailed to a most destructive degree, but no typhus. As to the general character of the epidemic, it appears to have been of the nature of the fever which has for so long a time existed in the country; but variously modified by the influence of the seasons, or, perhaps, by unknown causes. It seems highly probable, that what was once erroneously considered as the sole cause of epidemic fever, under the name of an epidemic constitution of the atmosphere, has existence, although imperceptible except in its effects. Another of the predisposing causes, and the most powerful of all, is the exhalation from animal substances in a state of putrefaction.
