VITALITY OF PUTEEFACTIVE OEGANISMS. 227 



wards. Of the two melon-flasks, one remained barren 

 and the other developed life. Of the two cucumber- 

 flasks, one became turbid, the other remained clear. Of 

 the four turnip-flasks, two became turbid and two re- 

 mained clear. Out of the ten flasks, therefore, all freely 

 connected with the external air, six remained perma- 

 nently barren. By further practice barrenness in almost 

 every instance has been secured. The conclusion, I 

 think, is obvious. It is not the heat alone that destroys 

 these germs, for fifty times the amount of heat will not 

 accomplish this when oxygen in due quantity is pre- 

 sent : the heat must be aided by the withdrawal of the 

 oxygen. 



§ 26. Mortality of Germs through excess of Oxygen. 



The foregoing remarks lead naturally to a brief 

 reference to the important experiments of M. Paul Bert* 

 on the toxic influence of compressed oxygen. From the 

 imperfect account of these experiments which first 

 reached me, I inferred that the germs of putrefaction 

 had been destroyed by mere mechanical pressure, and 

 more than a year and a half ago I placed turnip-infu- 

 sions in strong iron bottles, and subjected them for several 

 days to an air-pressure of twenty-three atmospheres. 

 When taken from the bottles the infusions were found 

 one and all swarming with life. Last October I made 

 a series of similar experiments with infusions of hay and 

 turnip, subjecting them for several days to an air-pres- 

 sure of twenty-seven atmospheres. When taken from 

 their iron bottles the infusions were found one and all 

 teeming with Bacteria. 



I then resorted to pure oxygen, and found the same 

 to be true of my infusions thatM. Paul Bert had found 

 ^ Comptes Kendiis, vol. Ixxx. p. 1579. 

 q2 



