No. II. 



Observations on the Laws governing the Communication of Contagious 

 Diseases, and the means of arresting their progress. By David 

 Hosack, M. D. Professor of the Theory and Practice of Physic and 

 Clinical Medicine in the University of the State of New-York, SCc. 



[Read before the Society, 9th June, 1814.] 



In July, 1808, I addressed to Dr. Chisholm some observations on 

 contagion, or infection.* The object of that communication was, if 

 possible, to narrow the ground of controversy upon that important 

 and much contested subject. This I endeavoured to do, first, by 

 showing that the distinction which had been proposed by some late" 

 writers, between contagion and infection, was unnecessary and fallacious ; 

 secondly, by dividing all diseases which are contagious, infectious, or 

 communicable from one person to another, into different classes, accord- 

 ing to the several laws which appear to govern their communication. 

 These classes are three in number. 



The first embracing those diseases which are communicated exclu- 

 sively by contact j as the itch, syphilis, hydrophobia, &c. which are never 

 conveyed through the medium of the atmosphere. 



The second including those diseases which are communicable both by 

 contact, or the near approach to the sick, and by the atmosphere, as 

 measles, small-pox, scarlet fever, &c which are communicable in every 

 season of the year, and in every climate ; in a pure as well as in an impure 



* See Edinburgh Med. and Surg. Journal, vol. 5. p. 247. American Medical and Philo 

 sophical Register, vol. 2. p. 14. 



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