Now, without doubting in the least that in some instances this may be the case, it seems to me quite obvious, from my own experiments, that a different interpretation may be given of Gruithuisen’s results--which I have myself verified,--and of the fact that meats and vegetables will often remain unchanged for years after having been heated in closed tins from which all air has been expelled.[88] [88] It was, indeed, the consideration of these latter facts which originally forced Gay-Lussac to the conclusion, that fermentation would not take place _in vacuo_, or without the presence of free oxygen, which was and still is, believed by many, to be the immediate determining cause of fermentation. If we ponder only upon the fact that certain fluids, in contact with a very small quantity of air, in an hermetically-closed vessel, will not undergo change; though these same fluids will change when exposed to a much larger quantity of calcined air, there may be strong reason for coming to an opinion similar to that of Gay-Lussac. When, however, it is also ascertained that provisions which have been subjected to the long-continued influence of heat, do not undergo change in closed vessels, if all air has been expelled from the _very small space above the level of the provisions_; though many organic infusions will putrefy if they occupy only one half, or less, of a hermetically closed vessel from which all air has been similarly expelled by ebullition of its fluid contents, it is impossible that the same explanation can hold good. And at the same time another interpretation is suggested for the first set of facts.