228 THE FLOATING-MATTER OF THE AIR. 



true of his flesh, moist bread, boiled starch, strawberries, 

 cherries, wine, and urine. Pressures varying from 

 twenty-seven atmospheres to ten atmospheres of oxygen 

 were employed. In all cases, however long the pressure 

 was continued, or however favourable to putrefaction the 

 surrounding temperature might be, the infusions (which 

 embraced those of beef, mutton, and turnip) were found, 

 when taken from the bottles, as clear as crystal and 

 entirely free from life. It required, indeed, long subse- 

 quent exposure to the common air to infect infusions 

 which had been thus surcharged with oxygen. Other 

 bottles containing the same infusions were simultane- 

 ously subjected to a like pressure, not of oxygen, how- 

 ever, but of atmospheric air. When removed from the 

 bottles they were one and all found in a state of putre- 

 faction and swarming with life. 



Thus when oxygen is wholly withdrawn from organic 

 infusions, the life with which we are here concerned 

 ceases. When, on the other hand, the gas is in con- 

 siderable excess, it becomes a deadly poison to organisms 

 which, in moderate quantities, it sustains. As in the 

 case of temperature, so in regard to the supply of oxygen, 

 there is a medial zone favourable to the play of vitality, 

 beyond which, on both sides, life cannot exist. 



The present memoir virtually ends here ; but I will 

 append a few brief sections which, though incomplete, 

 are not without instruction. 



§ 27. Experiments on neutralized Urine. 



I have already communicated to the Koyal Society 



the result of some experiments made with this liquid,* 



in which the potash employed for neutralization was 



subjected to a temperature of 220° Fahr. The alkali 



^ Proceedings, vol. xxv. p. 457. 



