February 29, 191 2I 



NATURE 



579 



the changes produced, and the diseases to be guarded 

 af^ainst in the subtle preparation of these different 

 articles of daily use that the author is concerned. 



The treatment of this varied assortment of subjects 

 is somewhat condensed, no doubt from limitations of 

 space, but the reader is supplied with a considerable 

 amount of information about each, much of which is 

 extremely interesting. In every case a useful outline 

 of the method of manufacture or preparation is given, 

 at all events as regards that stage of it in which 

 fermentation is involved. 



The treatment of the various processes dependent 

 on alcoholic fermentation is too condensed to be 

 entirely satisfactory, althoug-h all the essential points 

 are touched upon. A somewhat disproportionate 

 amount of space is devoted to the discussion of the 

 "bios" question, which, however interesting in itself, 

 is not of supreme technical importance. The fact, 

 first observed by Wildiers, that yeast when inoculated 

 in small amount into a synthetic medium fails to 

 grow, was explained by him as due to the absence 

 from such a medium of some specific material essential 

 for yeast growth, and to this unknown substance he 

 gave the name of bios. It is probable that the ex- 

 planation advanced by Pringsheim, that yeast can 

 only gradually adapt itself to the assimilation of the 

 nitrogen of such media, is correct, although it seems 

 also to be true that different yeasts possess very 

 varying degrees of adaptability. In view of these 

 facts it is remarkable that Pasteur was so successful 

 in his classical experiments on the growth of yeast in 

 simple media, and it has been suggested that this 

 success was due to the presence of mycoderma in his 

 yeast, the presence of this organism having been 

 found to enable yeast to grow freely in media such as 

 he employed. 



The function of fermentation processes in the pre- 

 paration of alcoholic beverages and vinegar is, of 

 course, the fundamental one of producing the essen- 

 tial constituent — the alcohol or acetic acid — by 

 biochemical change from the materials present in 

 the liquid employed. When we turn to the other sub- 



ances on our list, however, this is found to be by 



> means the case. Coffee consists of seeds or beans 

 A liich occur firmly embedded in an integument, the 

 whole forming the fruit of the plant. The chief 

 function of the fermentation in this case seems to be 

 the loosening of this integument, so that the beans 

 I rm readily be separated and dried, and this is effected 

 1(V the decomposition of a viscid layer immediately 

 -iirrounding the seeds, an alcoholic fermentation of 

 iliis material occurring first, and being followed by 

 .1 stage in which acetic acid is produced, a consider- 

 al)Io rise of temperature accompanying the change. 



Black tea and tobacco, on the other hand, are sub- 

 niitfod to processes of fermentation the object of which 

 is the attainment of the flavour and aroma upon which 

 their value depends. In both cases opinions are 

 divided as to the exact nature of the process. On one 

 li and it is maintained that micro-organisms are essen- 

 tial agents and it has even been proposed to impart 

 ilu- aroma of the finer qualities of tobacco to inferior 

 material by inoculation with the appropriate organ- 

 isms. On the other hand it is contended that the 

 NO. 2209, VOL. 88] 



change is enzymic, due to the decomposition of gluco- 

 sides and to oxidation processes, although it is ad- 

 mitted that organisms are present and may have 

 some secondary and minor effect on the result. In 

 the case of cocoa, too, some doubt exists as to the 

 relative share of plant enzymes and extraneous organ- 

 isms in the fermentation to which the beans are 

 submitted, and which results in a dry bean of good 

 flavour and colour. 



The preparation of mustard has been specially in- 

 vestigated by the author. A mixture of ground white 

 and black mustard seeds (respectively containing- 

 sinalbin and sinigrin) is treated with 2"5 per cent, 

 acetic acid, along- with salt and a mixture of spices. 

 The chief change which occurs is the decomposition 

 of the g^lucosides with the liberation of the mustard 

 oils. The mass is then left for a few days, ground 

 and bottled. Since the glucosides of mustard are 

 remarkably resistant to the attack of most bacteria 

 and the mustard oils are strong inhibitants of bacterial 

 growth, although not particularly powerful anti- 

 septics, it might be thought that mustard would be 

 free from liability to bacterial " disease." This is, 

 however, not the case, and the author has isolated 

 two species of sporing bacteria (B. sinapivorax and 

 B. sinaipivagus) which are capable of decomposing the 

 mustard glucosides, in one case with evolution of gas, 

 and occasionally cause serious loss to the manufac- 

 turer. The book, which, as will be seen, deals with 

 an extremely interesting subject, is provided with a 

 ,q-ood index and bibliography, and is adequately illus- 

 trated. A. Harden. 



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(i) Lchrbucli der Mathematik fiir Studierende der 

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(3) Untersuchungen ilber Oszillationstheoreme . By 

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(4) Die partiellen Differentialgleichungen der mathe- 

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(5) The Dynamical Theory of Sound. By Prof. 

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(6) A Logical Notation for Mathematics. By Robert 

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(7) Vorlesungen iiber Variationsrechnung. By Prof. 

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