INFTJSORIAL ANIMALCULES. 55 



distilled Avatev, in which I mixed various auinial and vegetable sub- 

 stances : I then closed it with a good cork, tlii'ough which I passed 

 two glass tubes, bent at right angles ; the whole being air tight. It 

 was next placed in a sand bath, and heated until the water boiled 

 violentlj', and thus all parts had i-cachcd a temperature of 212°. 

 ^Vliile the watery vapour was escaping by the glass tubes, I fastened 

 at each end an apparatus, which chemists employ for collecting car- 

 bonic acid ; that to the left was filled with concentrated sulphuric 

 acid, and the other with a solution of potash. By means of the 

 boiling heat, everything living, and all germs in the flask, or in the 

 tubes, were desti'oyed, and all access was cut off by the sulphmic 

 acid on the one side, and by the potash on the other. I placed this 

 apparatus before my window, where it was exposed to the action of 

 light, and also, as I perfoi-med my experiments during the summer, 

 to that of heat. At the same time I placed near it an open vessel 

 with the same substances that had been introduced into the flask, 

 and also after ha'^dng subjected them to a boiling temperatiu'C. In 

 order now to renew constantly the air within the flask, I sucked 

 with my mouth, several times a day, the open end of the apparatus, 

 filled with solution of potash ; b}' which process the air entered my 

 mouth from the flask through the caustic liquid, and the atmospheric 

 ah' from without, entered the flask through the sulphuric acid. The 

 air was of course not at all altered in its composition by passing 

 through the sulphuric acid, but if sufiicicnt time was allowed for 

 the passage, all the portions of living matter, or of matter capable of 

 becoming animated, were taken up by the sulphuric acid and 

 destroyed. From the 28th of May, till the beginning of August, I 

 continued, uninterruptedly, the renewal of the air in the flask, 

 without being able, by the aid of the microscope, to perceive any 

 li^-ing animal or vegetable substance, although, during the whole of 

 the time, I made my observations on the edge of the liquid; and 

 when, at last, I separated the different parts of the apparatus, I 

 could not find in the whole liquid, the slightest trace of Infusoria, of 

 conferva, or of mould. But all the three presented themselves in 

 great abundance, a few days after I had left the flask standing open. 

 The vessel which I placed near the apparatus, contained, the follow- 

 ing day, Vibriones and Monads, to which were soon added larger 



