€80 TYNDALL ON SPONTANEOUS GENERATION. 



particle from their clothes or bodies must be blown to the flasks, the opera- 

 tors first singe the pliers in a spirit lamp to destroy all attached germs or 

 organisms, and then snij) off the sealed end of the flask. In this way the 

 twenty-seven flasks are charged with clean, vivifying mountain air. The 

 fifty flasks are placed with their necks open over a kitchen stove in a tern-, 

 jjerature varying from 50° to 90° Fahrenheit, and in three days twenty- 

 one out of the twenty-three flasks opened in the hay-loft are found to be 

 invaded with organisms. After three weeks' exposure to precisely the same 

 condition, not one of the twenty-seven flasks opened in free air had given 

 way. JS^o germ from the kitchen air had ascended the narrow necks, the 

 flasks being shifted to produce this result. They are still in the Alps, as 

 clear (the speaker doubted not) and as free from life as they were when 

 sent off from London. Is not the conclusion, he asked, imperative that it 

 was not the air, but something in the air, which produced the effects observed 

 in the flasks placed in the hay-loft ? What is this something ? A sun-beam 

 glinting through a chink in the roof or wall, and traversing the air of the 

 loft, which Avas in free communication with an open door-wJay with the 

 outer air, would show this air to be laden with suspended dust particles. 

 Can they have been the origin of the observed life? If so, we are not 

 bound by all antecedent experience to regard these fruitful particles as the 

 germs of the life observed ? 



Pr, Tyndall proceeded to indicate the test of what he described as 

 one of the princij^al foundations of heterogeny as jjroraulgated in this 

 country. He would place before his friend and co-inquirer, the candid 

 medical critic before assumed, two liquids which had been kept for six 

 months in a sealed chamber exposed to o^^tically pure air. The one is a 

 mineral solution, containing in proper i^roportion all the substances which 

 enter into the composition of bacteria; the other is an infusion of turnip. 

 Both liquids are as clear as distilled water, and there is no trace of life in 

 either of them. A mutton choj), over which a little water has been poured 

 to keep its juices from drying up, has lain for three days upon a plate in a 

 warm room. It smells offensively. Placing a drop of the fetid mutton- 

 juice under a microscope, it is found swarming with the bacteria, which 

 live by putrefaction, and without which no putrefaction can occur. With 

 a speck of the swarming liquid, the clear mineral solution and the clear 

 turnip infusion are each inoculated. In twenty-four hours the transj^arent 

 liquids have become turbid throughout, and instead of being barren as at 

 first, they are teeming with life. The exiDeriment is now varied. Oj)ening 

 the back koor of another closed chamber which has contained for months 

 the pure mineral solution and the pure turnip infusion, into each is dropj)ed 

 a small pinch of laboratory dust. The effect is tardier than when the speck 

 of putrid liquid was emplo^'ed. In three daj's, however, after its infection 

 with the dust, the turnip infusion is muddy, and swarming as before with 

 bacteria. But what about the mineral solution, which in the first experi- 

 ment behaved in a manner undistinguishable from the turnip-juice? At 



