250 



NA TURE 



{Jan. i8, 1877 



living and reproducing in a saccharine liquid, the ques- 

 tion arose whether the common Penicillhun glauctis and 

 the Aspergillus glaucus could be transformed into the 

 true alcoholic ferments of beer or of wine, and the still 

 wider question of the conversion of one ferment into 

 another ; a question of vital importance to the brewer, 

 since, if this theory of the conversion of one kind of 

 ferment into another were proved to be true, the hope 

 of obtaining greater power over the results of his pro- 

 cess would be dashed to the ground, or at any rate such 

 power would only be obtained in the distant future. In 

 his researches upon this question, M. Pasteur availed 

 himself of the liquid proposed by his pupil, M. Raulin 

 (p. 89), e.g :— 



parts. 



We must refer the reader to M. Pasteur's book for the 

 full directions of procedure and the precautions to be 

 taken in order to avoid the introduction of mixed or- 

 ganisms. No one can read this portion of his work with- 

 out being greatly impressed by the author's wonderful 

 ability in detecting and overcoming difficulties and thereby 

 removing sources of error which have led so many to 

 erroneous conclusions. We may briefly sum up this part 

 of his work by stating that in no case where such neces- 

 sary precautions were taken did he ever find that the 

 penicillium changed to alcoholic yeast or to a mycoderma, 

 or that yeast gave rise to vibrios, or that mycoderma aceti 

 became yeast. M. Pasteur himself at one time thought 

 he had detected the conversion of the mycoderma vini 

 into a true alcoholic ferment ; in this, however, he now 

 finds he was in error, and that more rigorous precautions 

 fail to support his original supposition. 



In his experiments with mycoderma aceti and myco- 

 derma vini carried out with his usual marvellous ingenuity 

 and attention to details, he has shown that these organ- 

 isms in contact with the air burn up the sugar of the 

 liquid upon which they rest ; and so far from alcohol 

 being produced in quantities that may be detected, the 

 mycoderma vini completely burns up any alcohol pre- 

 viously existing in the liquid. When submerged in the 

 liquid, though life is far less active, they continue to exist 

 for a time, undergoing structural changes, obtaining the 

 necessary oxygen from the sugar, and producmg alcohol, 

 as in the case of the penicillium glaucus and aspergillus 

 glaucus under similar conditions of submersion. We 

 must admit, with Pasteur, that the production of alcohol 

 and carbonic acid from sugar, in other words, alcoholic 

 fermentation, is a chemical act attending the life of cells 

 the moment they are removed from the influence of 

 free oxygen, and are submerged in a saccharine liquid 

 capable of yielding oxygen and heat by its decom- 

 position. This alcohol-producing character becomes, 

 therefore, not the isolated property of this or that 

 organism, but a general function of a living cell, when 

 removed from the air and compelled to obtain the 

 necessary oxygen by the decomposition of its food. The 

 duration of life and the production of alcohol will vary 

 with the power of the cell to reproduce its kind under 

 these submerged conditions. I have already referred to 



the production of alcohol and carbonic acid when growing 

 malt is placed in an air-tight vessel. Under such circum- 

 stances alcohol and a large amount of carbonic acid are 

 for a long time produced, ultimately the moist mass 

 becomes increasingly acid, the production of alcohol 

 ceasing and acetic and other acids being formed attended 

 with a strong etherial odour. When first noticed by the 

 writer in the year 1873 he was unaware of M. Pasteur's 

 previous conclusions as to the action of vegetable cells. 

 Messrs. Lechartier and Bellamy in 1874 published their 

 valuable researches, upon which they had been engaged 

 for some time, and they proved incontestably that the 

 cells of fruits possessed the power, when removed from 

 free oxygen, of obtaining this gas by the decomposition 

 of sugar ; alcohol and carbonic acid gas being produced, 

 though not in the ratio found in true alcoholic fermenta- 

 tion. We thus learn from our author's researches, amply 

 confirmed by those of Lechartier and Bellamy, that active 

 living cells, when removed from the influence of free 

 oxygen, and when placed under conditions where they 

 must obtain it from saccharine materials, for a time con- 

 tinue to exist, producing alcohol and carbonic acid. 

 Those, such as the cells of fruits and grain, which cannot 

 reproduce under these conditions, soon die, and the 

 amount of alcohol produced is but small ; on the other 

 hand those cells which can reproduce by germination 

 become true ferments, and their action only ceases when 

 the original reproductive energy due to their previous 

 aerial condition also ceases. Thus when the inucor 

 racemosus was submerged in a saccharine liquid it was 

 found that the alcoholic fermentation was at first active 

 and then finally ceased, the cells being deformed in 

 contour, full of granulations, and to all appearance dead. 

 The introduction of a little pure air, however, rein- 

 vigorated the apparently dead organism, and agam — for 

 a time — alcoholic fermentation was produced. Free 

 oxygen therefore endows these simple cell-plants with an 

 energy which enables them for a time, longer or shorter, 

 to exist without it by obtaining the necessary oxygen 

 from their food. I have said for a tune, because the 

 mucor racemosus, or the mycoderma submerged in a 

 liquid soon lose their activity and cease to act, the true 

 yeast ferments under the same conditions being enabled 

 for a much longer period to reproduce and carry on their 

 vital functions ; even with these, however, Pasteur has 

 proved the necessity of periodical aeration so as again to 

 place them under their normal aerial condition, a fact 

 long known to those English brewers who employ 

 the method of rousing to stimulate the activity of the 

 yeast. Pasteur's investigations on fermentation have 

 convincingly proved— -at least to most minds — the intena- 

 bility of a peculiar motion and also of spontaneous 

 generation as being the true cause of these interesting 

 phenomena. 



In addition to a continued life without free oxygen 

 which the yeast cell manifests, there is another feature 

 — exceptional in character — which it possesses, and that 

 is, that its growth is not commensurate with the sugar ^ 

 decomposed. For a given weight of yeast formed one 

 may have ten, twenty, or one hundred times its weight of 

 sugar decomposed. It may be of interest to quote here 

 two experiments — out of many — bearing on this ques- 

 tion and also on the influence of dissolved oxygen in a 



