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principle regulating the rise, progress, decline, and consecutive 

 development of epidemics. 



In cases in which a special form of epidemic meteoration reigns 

 over many years, there are not unfrequently seasons in which its 

 peculiar agency is for a time suspended, or so broken up as to allow 

 of the intercurrence of other varieties of meteoration which, after 

 prevailing for a period of a longer or shorter duration, totally dis- 

 appear. Such intercurrences happened in New York in 1832 and 

 1834. In the warm months of these years the atmospheric condi- 

 tion, which had so long and actively promoted the prevalence of the 

 exanthemata, temporarily gave way, and in its place was developed 

 that peculiar meteoratious influence to which are referable the 

 ravages of the epidemic cholera. Of this disease 3513 persons 

 perished in that city in 1832, and 971 in 1834. 



Of the diseases arranged in the second class of epidemics, or those 

 denominated infectious, the committee must limit their observations 

 to those which have attracted most attention in the United States 

 during the past year. But before passing to the notice of these 

 diseases, it may be observed, that though intermittents, remittents, 

 and dysentery, arising from the mild sj)ecies of koino-miasma, have, 

 as in former years, prevailed more or less extensively in the districts 

 of country in which the atmospheric temperature and the geological 

 •formation and qualities of the earth's surface favour the generation 

 of that poison, there is nothing in their history, known to the com- 

 mittee, worthy of being specially recorded. These disorders in 

 their types, general characters and febrile phenomena appear to be 

 essentially the same in every year, while in the extent of their pre- 

 valence and their diathesis they are strikingly influenced by the 

 varying latent properties of the general atmosphere. 



From the ravages of epidemic yellow fever, produced by the second 

 or malignant species of koino-miasma, our country, with the exception 

 of the cities of New Orleans, Lafayette and Mobile, has been exempt 

 during the year 1847. The frequent though irregular periodical 

 occurrence of that form of pestilence in our southern cities, and its 

 occasional prevalence in our northern maritime towns, render every- 

 thing concerning it peculiarly interesting to American physicians. 

 Its epidemic relations to climate and soil, temperature and humidity, 

 the source and composition of its infectious principle, the nature of 

 the epidemic meteoratious influence which favours its prevalence, its 

 modifications, diagnostic phenomena, anatomical characters and 

 treatment, are topics which challenge the researches of philosophical 



