VriALITY OF PUTREFACTIVE ORGANISMS. 235 



Sixteen such chambers were employed, one of them 

 containing twelve test-tubes, each of the others only 

 three. There were therefore fifty-seven test-tubes in 

 all. The result of the experiment was, that out of the 

 fifty-seven tubes, twenty-seven became turbid in a few 

 days, while thirty remained for months without sensible 

 alteration.^ 



A considerable number of retort-flasks were charged 

 at the same time with the same infusions, and boiled for 

 five minutes in an oil-bath. The great majority of 

 these flasks remained perfectly intact. 



Here, then, as elsewhere, the ground on which the 

 doctrine of spontaneous generation has sought to plant 

 itself slips from under it ; for assuredly the scientific 

 mind will attribute to other causes than to it the pro- 

 duction of organisms in the minority of cases above 

 referred to. 



One likely cause may here be signalized and illus- 

 trated. The experiments of Spallanzani on the action 

 of heat upon seeds are well known, and they have 

 been frequently cited in support of the thesis that 

 the briefest exposure to the temperature of 212° Fahr. 

 suffices to destroy all living matter. I have repeated 

 many of Spallanzani's experiments, and will here 

 briefly refer to one series which bear upon the present 

 point. Peas, kidney-beans, cress- and mustard-seed 

 were tied up in small calico bags, and boiled for in- 

 tervals varying from half a minute to five minutes. 

 They were then carefully sown in flower-pots filled with 

 well-prepared earth, and placed in a shed kept at a 



' These chambers were prepared and their tubes charged prior 

 to the introduction of hay into our laboratory last autumn, other- 

 wise the immunity of a single one of them could not have been 

 secured. The chambers employed had stood over from my last in- 

 vestigation, and no pains had been taken to render them air-tight. 



