SPONTANEOUS GENERATION 341 



the way of this fact, established as it has been by hun- 

 dreds, 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 opti- 

 cally 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 swarming with the bacteria of putrefaction. With 

 a speck of the swarming liquid I inoculate the clear min- 

 eral 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 throughout, and instead of being barren as at first 

 they are teeming with life. The experiment may be re- 

 peated 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 infec- 

 tion any one of a hundred other putrid liquids, animal or 



