106 



It thus appears, that in the first twenty of the last forty-three 

 years, scarlet fever was nearly extinct in the city of New York; and 

 that measles and small-pox were sporadic ; and further, that in the 

 last twenty-three years, these fevers have prevailed to an extent and 

 in a mode which characterize epidemics. In contemplating the gra- 

 dual decrease of the exanthemata since 1837, may we not infer that, 

 at a period not very distant, they will become as rare, in proportion 

 to the population, as they were from 1805 to 1823 ? 



In connection with these facts, we would notice a circumstance in 

 the history of an infectious epidemic disease, which is deemed worthy 

 the attention of those engaged in researches concerning the pheno- 

 mena and laws of popular diseases. It is this; whilst the scarlet 

 fever, measles, and small-pox were of infrequent occurrence in New 

 York, the yellow fever prevailed several times epidemically in that 

 city, and the fear of its annual visitation was never absent from the 

 public mind. Since 1822, or, in other words, since the exanthemata 

 have been prevalent, the yellow fever has not appeared as an epide- 

 mic in New York, or in any place north of Charleston. 



From these facts it seems that yellow fever and the exanthemata 

 owe their prevalence to very different varieties of epidemic me- 

 teoration. If this be true, is there not reason to apprehend that 

 when the prevalence of scarlet fever, measles and small-pox shall 

 have further declined or ceased, yellow fever will reappear epi- 

 demically in our great northern emporium and the neighbouring 

 cities? The fact is remarkable, that the years, from 1804 to 1823, 

 in which yellow fever prevailed in New York, are among those in 

 which the fewest deaths are recorded from the exanthemata. The 

 years referred to are 1805, 1809, 1813, 1819 and 1822. In the 

 last of these years the yellow fever was more extensively epidemic 

 than it had been since 1805 ; and there was but one death reported 

 from scarlet fever, one from measles, and none from small-pox. 



It must not be supposed, from what has been said, that the pro- 

 gressive development, duration, and transition of the meteoratious 

 influences which have favoured the prevalence of yellow fever and 

 the contagious exanthemata in New York, are attributable to the 

 operation of a general principle which everywhere governs and 

 establishes a uniformity in the succession of epidemics, or, in other 

 words, which illustrate the order of the epidemic prevalence of the 

 diseases in question, as they occur in other localities, or in a different 

 series of years in the same place. There appears to be no such 



