588 flUQMaTS OP SCIENCE. 



However this may be whatever be the state of the sur- 

 face of the body, of the spores of Bacillus subtilis, they 

 do as a matter of certainty resist, under some circum- 

 stances, exposure for hours to the heat of boiling water. 

 No theoretic skepticism can successfully stand in the wa 

 of this fact, established as it has been by hundreds, if not 

 thousands, of rigidly conducted experiments. 



We have now to test one of the principal foundations of 

 the doctrine of spontaneous generation as formulated in 

 this country. With this view, I place before my friend 

 and co-inquirer two liquids which have been kept for six 

 months in one of our sealed chambers, exposed to optically 

 pure air. The one is a mineral solution containing in 

 proper proportions all the substances which enter into the 

 composition of bacteria, the other is an infusion of turnip 

 it might be any one of a hundred other infusions, 

 animal or vegetable. Both liquids are as clear as distilled 

 water, and there is no trace of life in either of them. 

 They are, in fact, completely sterilized. A mutton-chop, 

 over which a little water has been poured to keep its juices 

 from drying up, has lain for three days upon a plate in our 

 warm room. It smells offensively. Placing a drop of the 

 fetid mutton-juice under a microscope, it is found swarm- 

 ing with the bacteria of putrefaction. With a speck of 

 the swarming liquid I inoculate the clear mineral solution 

 and the clear turnip infusion, as a surgeon might inoculate 

 an infant with vaccine lymph. In four-and-twenty hours 

 the transparent liquids have become turbid through- 

 out, and instead of being barren as at first they are 

 teeming with life. The experiment may be repeated a 

 thousand times with the same invariable result. To the 

 naked eye the liquids at the beginning were alike, being 

 both equally transparent to the naked eye they are alike 

 at the end, being both equally muddy. Instead of putrid 

 mutton-juice, we might take as a source of infection any 

 one of a hundred other putrid liquids, animal or vegetable. 

 So long as the liquid contains living bacteria a speck of it 

 communicated either to the clear mineral solution, or to 

 the clear turnip infusion, produces in twenty-four hours 

 the effect here described. 



We now vary the experiment thus: Opening the back- 

 door of another closed chamber which has contained for 



