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converted into an infectious agent, capable of producing 

 disease in a fresh portion of a solution of sugar, that is, of 

 effecting its transformation. In the same manner I believe 

 that during the continuance of all those diseases really 

 arising from malaria, a fresh amount of exciting agents, 

 similar in character to the one originally derived from the 

 putrid source, is generated in the blood and other vital parts; 

 and that it may spread from a diseased subject and produce 

 a continuance of the malady in the same manner as it may 

 radiate from a putrid drain. 



I am aware that chemical and other experiments have been 

 made, with a view to prove the non-existence of any matters 

 in the air of rooms occupied by fever patients different from 

 those naturally contained in the external atmosphere ; yet the 

 peculiar odour perceived in all such rooms might have con- 

 vinced the experimentalist that something foreign was present, 

 and that their conclusions were erroneous. It is not by a 

 simple analysis of the air that we must expect to find these 

 highly-rarefied compounds; it is only by searching for them 

 in the moisture condensed from the atmosphere in contami- 

 nated localities that we can hope to discover their presence, 

 and learn their properties; and I do not despair, if this 

 course be pursued, of seeing all these matters exhibited in 

 such a tangible form as will effectually clear up the mystery 

 which has hitherto hung over them. I am aware that 

 Queckete, and other eminent physiologists, would attribute 

 the action of malaria, and, I believe, all infectious agencies, 

 whether communicated through the air or by mere contact, 

 to the presence of mycelium, a microscopic germ or spore, 

 capable of reproducing itself with great rapidity, wherever 

 it finds a suitable soil for its development. I am too well 

 aware of the presence of such spores, and their rapid growth 

 and re-production during the vinous fermentation, and of 

 many other instances in the vegetable kingdom, entirely to 



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