FERMENTATION 145 jected to the action of filtered and heated air and oxygen without the production of fermen- tation ; and they have also introduced the pulp of fruits into boiled must, with the same result when it was excluded from the presence of un- filtered air. Fermentation has also been car- ried on in tubes having their ends closed by thin membranes, and placed in fermentable liquids, but without exciting in the latter any fermentation except when natural air was ad- mitted, which, it is contended, always carries the germs of ferments. M. Fremy maintains that certain experiments which he has made controvert the position of the upholders of the physiological theory. At a session of the French academy of sciences held in October, 1872, a discussion of the subject took place between M. Pasteur and M. Fremy, in which the latter contended that the influence of at- mospheric dust in the phenomena of fermenta- tion is only secondary and accidental, and that the true origin of ferments is in the mass of the fermentable substance. Fremy is disposed to believe that Pasteur did not establish fer- mentation in the boiled must in which he had placed grape juice, because he placed it in other conditions, besides those of exclusion of air, in which alcoholic fermentation could not take place. He recounted some experiments which he had made, among which was the following : He squeezed the pulp of some pears and other lits, but without breaking the skins, and )lacing them in favorable situations, found at end of several days that they contained stable quantities of alcohol ; fermentation laving been produced in the interior of the lit where, in his opinion, the dust of the air mid not exert any influence. Fremy there- fore believes that the parenchyma of fruits con- iins the material which is capable of taking conditions by which it may form ferments, [e contends that there is a great number of lents that are neither organized nor living, rhich are capable of producing various kinds fermentation, depending upon the conditions which the fermentable matter is placed, -.iebig compares the action of a ferment to lat of heat, by .which the atomic constituents )f organic molecules are shaken asunder and ift to recombine under the influence of forces that may be present. Acetic acid is separated ")y heat into carbonic acid and acetone ; just sugar is separated by yeast into carbonic
- id and alcohol. He regards vital action and
lemical action as phenomena which must be sidered separately in seeking an explana- tion of fermentation, and holds that the fact it yeast causes fermentation in a pure so- ition of sugar is opposed to the idea that the lecomposition of sugar is caused by the devel- )pment and increase of yeast cells ; for yeast msists chiefly of a substance containing nitro- ?n and sulphur, besides phosphates, and these lot be furnished by the sugar ; and more- )ver, beer yeast causes a similar decomposition
- f other substances, malate of lime being con-
verted into carbonic acid, acetate, carbonate, and succinate of lime. Salicine is also decom- posed by yeast into saligenine and salicylic acid ; " and a similar decomposition of salicine is produced by emulsine without any recogni- zable physiological process being concerned in the change. Emulsine acts upon amygdaline in like manner, its effects being recognizable in a few minutes by the new products. Emulsion of sweet almonds also undergoes active vinous fermentation when mixed with grape sugar. But if substances containing sulphur and nitro- gen, like emulsine, are, by reason of alteration in the arrangement of their atoms, capable of inducing change in other organic molecules, so that they separate into new products, there is reason for suspecting that in the action which yeast exerts upon sugar its sulphuretted and nitrogenous constituent plays a similar part." On the other hand, the experiments of Hallier are more in support of the views of Pasteur. According to this observer, the same germinal molecules develop, according to the nature of the fermentable substances in which they are deposited, into the fungoid forms peculiar to each fermentation. The forms which induce putrefaction, fermentation, and mildew are all varieties of one another. When they are de- veloped within the fluids they are cellular for- mations, but when they grow upon the surface they produce fructification. Hallier agrees with Pasteur's view that the germs are all carried by the air. The following, condensed from the " Quarterly Journal of Science," is a brief sum- mary of Hallier's views. The most abundant source of germs appears to be the penicillium crustaceum (fig. 4), whose spores are universal- ly spread because it is more hardy, more fertile, and develops at lower temperatures than others of its kind. A spore of penicillium falling into a watery fluid bursts into a multitude of parti- cles, each of which may be the radicle of a living fungus. The minute particles unite in twos, forming a double cell, and divide with great rapidity. (See fig. 5.) The minute parti- cles then unite in chains, constituting lepto- thrix, which is not a species, but a form of vege- tation common to many species. In pure water development can go no further, and after a few FIG. 4. Fructification of Penicillium crus- taceum (Hallier). FIG. 5. Spores of Penicillium crus- taceum bursting in water and setting free their contained par- ticles, micrococci, which unite in rows or chains (Hallier). hours the organisms cease to be formed, the presence of a nitrogenous substance being ne- cessary for further development. The minute spherules, micrococci, are the special ferment of putrefaction. In the presence of sugar the spherule enlarges and becomes a nucleated cell,
