28 



A hood dipping into quicksilver answers 

 excellently. Yet mere filtration is inadequate. 



I am now certain that this much talked of 

 spontaneous generation is largely a delusion 

 and that if the phenomenon ever does take 

 place it is only exhibited under extremely un- 

 usual conditions and in most extraordinary 

 cases. I am also aware that Kircher ascribed 

 the virulence of the Plague to the action of 

 living creatures — you will find his assumption 

 elaborated upon in his scarce and curious 

 "Scrutinum Contagiosse," published nearly a 

 century and a half ago — but he entirely failed 

 to prove his theory by recourse to experiments 

 (I have made many) and deduce from them 

 many things they made manifest to me. 



It is one thing to hint, to guess, to prophesy, 

 but quite another, I assure you, to be able to 

 truthfully say "I know," and then to connect 

 the vague and formless spirit of the Theory 

 with the definite and tangible Matter of Fact. 



This I may modestly assert I have done. 



I have placed some of the matter contain- 

 ing certain of what I have found to be the 

 minute beings causing the putrid sore throat 

 in the common calves foot jelly so familiar to 

 all of you and covered this with a bell jar 



