HOSACK ON THE LAWS OF CONTAGION. 22& 



little infection:" indeed, the extension of this disease, as has already 

 been frequently observed, was so circumscribed within the limits of this 

 impure air that it became very generally believed that, in that season, 

 whatever may have been the case in former years, the disease exclusively 

 arose from those domestic sources, more especially from the putrid 

 provisions. But that the yellow fever of that season did not derive its 

 origin from the spoiled beef is evident, not only from the fact, that the 

 disease had already previously appeared in other parts of the town, and 

 even in that very neighbourhood, before those heavy rains had fallen, 

 and their pernicious effects were perceived ; but also, that those tainted 

 provisions, unaccompanied with the specific poison of the disease, did 

 not of themselves communicate infection to those who were constantly 

 exposed to their effluvia. 



Mr. Edmund Prior, the inspector-general of beef at that time, in- 

 formed me, that of forty persons whom he had employed in examining 

 the beef, and in removing and emptying such barrels as were found in a 

 putrid state, not one was taken ill of the yellow fever.* But Dr. Chis- 

 holm and Dr. Stewart have abundantly shown, that decomposed animal 

 or vegetable matters will not, of themselves, produce the pestilence ;t 

 and that this disease is generated in the human system, and communi- 

 cated from one person to another, by a peculiar secretion from the 

 morbid body. My object is to show that when such virus is introduced 

 into a certain state of atmosphere, the disease is readily contracted, but 

 that beyond that atmosphere it is rarely infectious. 



Although the diseases which have been noticed are rarely communi- 

 cable in pure air, and are not generally contagious in the country, it is 

 not less true, that in some few instances it appears, either that the virus, 



See Note D. f See Note E. 



31 



