72 STUDIES ON FERMENTATION. 



The preceding series of experiments shows us that, in the 

 case of wort exposed to the air, germs of divers organisms, 

 amongst which various ferments — butyric, lactic, and alcoholic — 

 are to be found, fall simultaneously from the particles of dust 

 floating in the air. We must observe, however, that we were 

 dealing with the air of a laboratory in which we were constantly 

 studying analogous fermentations, and that a different atmo- 

 sphere would, most likely, give us different results. We shall 

 see a proof of this in the following paragraph, where we shall 

 also find some new facts tending to prove that the germs of 

 alcoholic ferment do not exist amongst the particles of dust 

 floating in the air, in anything like the quantity usually 

 supposed. 



§ V. — New Comparative Studies on the Germs held in 

 Suspension by the Air of Different Places which 

 are near each other, but Subjected to Different 

 Conditions affecting the Production and Diffusion 

 OF THE Particles of Dust found in them. 



We may compare the character and the greater or less abun- 

 dance of similar germs existing in neighbouring localities, by 

 studying the changes which take place in similar liquids exposed 

 simultaneously to the action of the air in those localities. To 

 do this, we must prepare a large number of flasks of the same 

 size, free from air, and containing about equal quantities of a 

 particular liquid^ — the same being used for all. We must open 

 the same number of these flasks in each of the localities we 

 have selected, and permit the air with all its particles of dust 

 . to rush into them ; then we must close our flasks again, and 

 observe, day by day, the appearances they present. The 

 results obtained by these means will not furnish us with con- 

 clusions applicable to every kind of germ that the air contains 

 at any given moment, but only with conclusions which apply to 

 those germs which can develop in the particular liquid em- 

 ployed. Thus, for example, we could draw no inference as to 

 the nature and relative number of bacteria or vibrios, in the 



