20 THE BEGINNINGS OF LIFE. 



pretty evident. Germs and atmospheric particles being 

 equally got rid of in both modes of experimentation, 

 the great difference between them is that the weight of 

 the atmosphere is also got rid of in my experiments — 

 the fluids being contained In 'vacuo. But, as I have 

 already pointed out i, it has been ascertained by Mr. 

 Sorby, that pressure undoubtedly influences '^chemical 

 changes taking place slowly,' and such as are therefore 

 ^probably due to weak or nearly counterbalanced 

 affinities;"' and it has also been shown that 'pressure 

 will more or less influence such chemical actions as are 

 accompanied by an evolution of gas, so that it may 

 cause a compound to be permanent, which otherwise 

 would be decomposed.' But, if increase of pressure 

 retards, a diminution of pressure may be expected to 

 facilitate such chemical changes, so that one can only 

 explain the results which I have obtained, on the 

 ground that many boiled fluids, which will not undergo 

 change when protected from the influence of atmo- 

 spheric particles (living or not living) at the same time 

 that they are subjected to ordinary or increased pressure, 

 will, on the contrary, pass through such changes when 

 pressure is diminished, by the fluids being preserved 

 in vacuo '^. It is not pretended that this is a rule 

 applicable to all fermentable fluids — far from it ^, 



^ See vol. i. p. 350. 



^ On this subject, see vol. i. pp. 418-420. 



3 I very soon convinced myself, in fact, that diminution of pressure 

 exercised very little effect over tlie changes which take place in solutions 



