Apeil 17, 1896.] 



SCIENGE. 



601 



great industries. Having been successfully 

 outlined in Jorgensen's admirable text-book, 

 ' Micro-organisms and Fermentation' (London, 

 1893), they are now presented to tbe public as 

 exhaustively as necessary to the practitioner 

 as well as to those who, without being zymo- 

 technics ex-professo, need to become acquainted 

 with the original work of Hansen. 



The present volume ' treats, ' as the author 

 expresses himself, ' in the main, of the great 

 questions of the circulation in nature of the 

 alcoholic fungi, their relationship to the diseases 

 of beer, the pure cultivation of yeast, and the 

 employment of systematically selected species 

 and races. ' 



Until the beginning of the last decennium 

 the fermentation of beer, wine, etc., the sour- 

 ing of milk, and other procedures involving an 

 employment of the vitality of micro-organisms, 

 were carried out more or less at random. 

 Pasteur taught us that if the fermentation in 

 beerwort shall terminate in the formation of a 

 fair product, no bacteria must be present in the 

 yeast. Thus, Pasteur's 'pure yeast' refers to 

 yeast free from bacteria. Hansen went further 

 than this. Having discovered the scientific 

 reasons why yeast is not constant with reference 

 to its morphological and physiological peculiar- 

 ities, he established the maxime, now generally 

 accepted, that yeasts, as commonly used in 

 breweries, are mixtures of cultivated and un- 

 cultivated species of Saccharomyces, and that 

 most of the latter so-called ' wild ' forms are 

 'disease '-producing, that is, give rise to fer- 

 mentations unfavorable to both producers and 

 consumers. They were found to cause — aside 

 from certain bacteria which are known to im- 

 pair the results of fermentations in the brewery 

 — many of the symptoms which are familiar to 

 hrewers, such as bitter taste and disagreeable 

 odor, lack of constancy in the product, and the 

 like. 



Hansen's studies resulted directly in a method 

 by which it is in the power of any brewery to 

 secure a uniform, good product. Systematic- 

 ally selected culture yeasts would, when intro- 

 duced into the brewing establishments, be cer- 

 tain to yield uniform, good grades of beer. 



The proper selection of races was facilitated 

 iby a new method of pure cultivation, allowing 



the observer to trace the development of cultures 

 from individual well-defined cells.* 



The successful introduction of Hansen's sys- 

 tem into nearly all countries speaks eloquently 

 for its merits. 



The major part of the volume refers to the 

 practical side of the question, but, as it is based 

 upon new methods in the study of microscopic 

 fungi, considerable space is devoted also to the 

 botanical study of these, especially of the yeasts. 

 Hence the appropriate sub-title noted above. 



The indirect result of Hansen's work is a new 

 departure in the dairy industry. Storch, of 

 Copenhagen, applied the principle of selected 

 species of organisms to the ripening of cream, 

 and was followed by a number of able investi- 

 gators, among whom is Professor Conn, of this 

 country, who demonstrated the necessity of 

 selecting such forms of the lactic acid bacteria 

 as were found to produce an ideal ripening for 

 rational dairying. In this manner improved 

 grades of butter may be produced and main- 

 tained. 



The publications of Wortmann and others 

 show that the question of pure cultivation of 

 wine yeasts is rapidly gaining in favor and influ- 

 ence with the German and French manufacturers 

 of wines. 



In distilleries the system has also been suc- 

 cessfully adopted. 



Hansen's late studies of the acetic bacteriaf 

 seem to indicate a rapidly advancing reform in 

 the manufacture of vinegar, based upon the 

 same principle as has been followed year after 

 year by agriculturists throughout the world, 

 namely, that pure seed secure a pure crop. 



Space does not permit a recapitulation of the 

 substantial volume before us. Yet it is evident 

 that every one whose work in any respect 

 touches upon fermentations will find it among 

 those publications which must inevitably be 

 consulted in all future work. 



*This method was described exhaustively by the re- 

 viewer in the American 3Ianihly Mieroacopical Journal, 

 XV., 35—40, 1894; with plate. 



t Comp. rend. d. trav. du lahoratoire de Carlsberg 

 III., 265-327,1894. Bar. d. DeutschenBot. Ges. XI., 

 (69j-(73), 1893. See also Lafar ; Centralbl. f. Bakt. 

 ■a. Par XIII., 684-697, 1894 ; idem, zweite Abthei- 

 lung, I., 129-150 ; 1895. 



