doctrines of fermentation--it could not possibly help us to decide whether living or dead ferments were necessary. Dead organic particles would sink in still air in the same manner as living organisms;[77] and similarly, dead organic particles, have been shown to be less and less numerous in the atmosphere in proportion to the elevation obtained.[78] In these latter experiments M. Pasteur made use of yeast-water (alone or sweetened), and of urine--all three of them fluids, which, after having been boiled, are apt to possess only the second degree of fermentability. Shortly afterwards, M. Pouchet, in concert with MM. Joly and Musset,[79] repeated these experiments, with the sole difference that they employed strong infusions of hay--which experiment has shown almost invariably to possess the first degree of fermentability. And seeing that all their flasks, after a time, yielded organisms from whatever mountain elevation the air had been taken--the combined evidence tends strongly against the view of M. Pasteur. Since the germs in the fluids and in the flasks, in each set of experiments, had been previously destroyed by ebullition, and since in each set, also, air of the same character had been admitted to the boiled fluids, the different results seemed to show that fermentation or non-fermentation, in such cases, depends wholly upon the quality of the fluids employed. [74] Loc. cit. p. 71. [75] Loc. cit. pp. 75 and 76. [76] Loc. cit. pp. 83 and 84. [77] The subsidence of the atmospheric particles has been ably demonstrated by Professor Tyndall.--See ‘Nature,’ 1870. [78] See M. Pouchet’s ‘Nouvelles Expériences sur la Génération Spontanée,’ &c., p. 69. [79] See various communications in ‘Compt. Rend.’ (1863), t. LVII.