308 On Malaria. 



been known to occur in such situations.* Another proof, and it is 

 deemed sufficient, is the fact, that when the bodies of the Cimetiere des 

 Innocens, which were in every stage from incipient putrefaction to com- 

 plete decomposition, were disinterred and reinhumed, not a case of 

 fever appeared during the whole operation, w hich occupied two years. 



I cannot see any reason to deny that some deleterious exhalation 

 may originate in the materials which form the mud of marshes, and 

 which every where support vegetation, except, that it is unascertaina- 

 ble by chemical analysis ; and further, that the pestilential agent is 

 subdued by frost. There is no evidence that mineral or earthy sub- 

 stances contribute in any degree to malaria, except clay, which, by 

 preventing the subsidence of water, remotely causes the maceration 

 of plants, and a consequent disengagement of malarious effluvia ; 

 but this being purely a mechanical cause, the quality of the effluvia 

 cannot in any degree be referred to the clay. 



It must be inferred that some foreign principles are evolved by the 

 moisture in these pestiferous exhalations, because pure water pro- 

 duces no deleterious effects. f The spray of cataracts is not un- 

 healthy, and sea fogs, J the mists which occur in thaws, or on high 

 mountains, or in high northern latitudes, are never followed with un- 

 favorable consequences. But whatever it is, whether a combination 

 of agents, or a single agent, it appears to have a vegetable origin, and 

 by its chemical union with water, or its elements, a new entity is pro- 

 duced, which is a poison, and which, being exhaled, constitutes the 

 marsh miasmata, or malaria. 



Some naturalists have conjectured that electricity has an agency in 

 this specific poison ; " but nature accomplishes her Avonders, not by 

 employing a multitude of agents, but by merely varying the combi- 

 nation of a few simple means," and from what we know of electrical 

 phenomena, it might be expected to exercise a salutary influence, by 

 agitating the atmosphere, and dispersing the mephitic vapors. 



That^ea^ is essential to its extrication, is proved by the increased 

 virulence of the miasma after the hot season, and the greater vio- 



*Many examples might be adduced, such as various processes in making leather, 

 manufacturing glue, catgut, &c. and above all, in Paris, the occupation of the 

 Knackers, a set of men who apply dead horses to useful purposes, but among whom 

 no endemic fever has been known to occur. 



I I think Dr. Fordyce maintains erroneously that it is the dampness alone of 

 marshes, which causes fever. 



X Witness the fogs on Rhode Island and Newfoundland. The'former place is dis- 

 tinguished for salubrity, and is resorted to by strangers for a summer residence. 



