102 ORIGIN OF LOWEST ORGANISMS. 



the re-entering air, when some of the same fluid will 

 putrefy, if placed under different conditions by which 

 it is freed both from the influence of the atmosphere 

 and from its germs L <?., when, instead of filtering the 

 re-entering air, no air is permitted to enter. Germs 

 and atmospheric particles being equally got rid of in 

 both sets of cases, 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 

 vacua. Now it has been ascertained by Mr. Sorby, that 

 pressure undoubtedly influences " chemical changes 

 taking place slowly, and therefore, probably due to 

 weak or nearly counterbalanced affinities;" and he 

 also states, in the Bakerian Lecture for 1863,* that 

 " a considerable number of facts have been described, 

 showing 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 per- 

 manent, which otherwise would be decomposed." If 

 increase of pressure retards, a diminution of pressure 

 will 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 atmosphe- 

 ric particles (living or not living) at the same time that 

 they are subjected to ordinary or increased pressure, 



* ' On the Direct Correlation of Mechanical and Chemical 

 Forces.' Proceedings of the Royal Society, vol. xii. pp. 539 

 and 546. 



