ADDITIONAL NOTES ON CONTAGION, 275 



deny contagion being incident to it. It requires a certain putrid state of the atmosphere 

 as a conductor, in order to impart it : and it may inoculate and assimilate any confined 

 portion of atmosphere which has been exposed to the requisite causes of contamination, 

 so that every part of it shall have power to communicate the poison. In the pure 

 atmosphere of the country the poison is commonly so diluted, that it is too weak to 

 excite the fever, except under peculiar circumstances. 



In every instauce in which yellow fever has been introduced into Philadelphia one 

 circumstance has invariably taken place : after the persons who have first taken the 

 disease have either died, or recovered, there has been an interval of health for several 

 days, usually from ten to thirteen or fourteen, before the alarm has been renewed. From 

 this circumslance, I have concluded, that during that space of time the infection secretly 

 works in the blood before it appears in fever. Often there is a second interval of appa- 

 rent health, but not of so long continuance. I hope that your view of the subject will 

 carry more conviction with it than we have hitherto perceived ; and I hope it will even 

 contribute, among the more sensible part of the profession, who do not think merely by 

 authority, to unite jarring opinions, and to settle common principles. 



SAMUEL S. SMITH. 



By physicians v;\io have recorded our epidemics such interval has been repeatedly 

 observed. In Dr. Caldwell's Essay on the Yellow Fever of Philadelphia of 1805, it is 

 very circumstantially noticed by that ingenious and able writer. 



NOTE L. (See page 236.) 



In the official document of the Board of Health of New- York, published on the 14th 

 of September, 1805, they thus addressed the inhabitants of this city: " The board 

 have formed a decided opinion, that the principal seat of the prevailing disease [the 

 malignant epidemic fever] is that part of the city included between Burling-slip and Old- 

 slip as far west as Pearl-street. Almost all the cases of disease which have occurred, 

 can be distinctly traced to a communication with that part of the city. It is a matter 

 of extreme regret, that the repeated admonitions of the board, to remove from this quar- 

 ter, have been disregarded by a number of individuals who have remained the self-devoted 

 victims of disease and death. They conceive it their duty again to enjoin it upon their 

 fellow citizens, who have continued there, to remove immediately." Again, and in the 

 same address : " All persons who do not comply forthwith with this advice of the board, 



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