We find this fact, which we published as long ago as 1863, confirmed in a work of H. Hoffmann’s published in 1869, under the title _Mémoire sur les bactéries_, which has appeared in French (_Annales des Sciences naturelles_, 5th series, vol. xi.). On this subject we may cite an observation that has not yet been published. Aërobian bacteria lose all power of movement when suddenly plunged into carbonic acid gas; they recover it, however, as if they had only been suffering from anæsthesia, as soon as they are brought into the air again. Footnote 149: These doubts might easily be removed by putting the matter to the test of direct experiment. Footnote 150: ROBIN, _Sur la nature des fermentations_, &c. (_Journal de l’Anatomie et de la Physiologie_, July and August, 1875, p. 386). Footnote 151: LIEBIG, _Sur la fermentation et la source de la force musculaire_ (_Annales de Chimie et de Physique_, 4th series, t. xxiii. p. 5, 1870.) Footnote 152: It is important that we should here remark that, in the fermentation of pure solution of sugar by means of yeast, the oxygen originally dissolved in the water, as well as that appropriated by the globules of yeast in their contact with air, has a considerable effect on the activity of fermentation. As a matter of fact, if we pass a strong current of carbonic acid through the sugared water and the water in which the yeast has been treated, the fermentation will be rendered extremely sluggish, and the few new cells of yeast which form will assume strange and abnormal aspects. Indeed this might have been expected, for we have seen that yeast, when somewhat old, is incapable of development or of causing fermentation, even in a fermentable medium containing all the nutritive principles of yeast, if the liquid has been deprived of air; much more should we expect this to be the case in pure sugared water, likewise deprived of air. Footnote 153: DOEBEREINER, _Journal de Chimie de Schweigger_, vol. xii. p. 129, and _Journal de Pharmacie_, vol. i. p. 342. MITSCHERLICH, _Monatsberichte d. Kön. Preuss. Akad. d. Wissen. zu Berlin_, and _Rapports annuels de Berzelius_, Paris, 1843, 3rd year. On the occasion of a communication on the inversion of cane sugar, by H. Rose, published in 1840, M. Mitscherlich observed: “The inversion of cane sugar in alcoholic fermentation is not due to the globules of yeast, but to a soluble matter in the water with which they mix. The liquid obtained by straining off the ferment on a filter paper, possesses the property of converting cane sugar into uncrystallizable sugar.” BERTHELOT, _Comptes rendus de l’Académie_. Meeting of May 28th, 1860. M. Berthelot confirms the preceding experiment of Mitscherlich, and proves, moreover, that the soluble matter of which that author speaks may be precipitated with alcohol without losing its invertive power.