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NATURE 



[^an. 16, 1890 



results of the experience acquired by themselves and 

 others. The writer notices their description of a process 

 for the estimation of arsenic in minerals and metals, 

 which was devised by himself for use in works ijnder his 

 control, that has not hitherto been published. It consists 

 in the separation of arsenic from its associations, by 

 distillation with ferric chloride mixed with calcium 

 chloride, and subsequent titration of the distillate by 

 iodine. The authors are mistaken in stating that there is 

 a difficulty in obtaining ferric chloride free from arsenic. 

 Even if there were difficulties, it is obvious that the 

 process itself affords a ready means of eliminating arsenic 

 from the ferric chloride mixture, before using it in the 

 actual assay. In this and one or two other cases, there 

 is a tendency to adopt the always undesirable method of 

 "blank" experiments to correct error arising from the 

 use of impme reagents, rather than whenever practicable 

 lo avoid the source of danger by the use of pure materials. 

 These are, however, hardly noticeable blemishes in a 

 really meritorious work, that may safely be depended 

 upon by those using it either for systematic instruction 

 or for reference. Thomas Gibb. 



BREWING MICROSCOPY. 



The Microscope in the Brewery and Malt House. By 

 Chas. Geo. Mathews, F.C.S., F.I.C., &c., and Francis 

 Edw. Lott, F.I.C., A.R.S.M., &c. (London and Derby : 

 Bemrose and Sons, J 889.) 



THERE are certainly few industries the growth and 

 development of which have been more influenced 

 by the progress of pure scientific discovery than those of 

 the brewer and distiller. These industries, formerly 

 carried on upon purely empirical lines, handed down 

 from father to son through countless generations, have 

 in recent years, through the advances in chemical and 

 biological science, been so transformed that their suc- 

 cessful conduct at the present time requires a most 

 thorough acquaintance with the leading principles of 

 these sciences. As a consequence of this change, we 

 find an increasing tendency for these industries to be- 

 come concentrated in a smaller number of hands each 

 producing on a larger and larger scale. The small 

 brewer himself lacking the necessary scientific training, 

 and not able to afford the requisite skilled assistance, 

 gives way before the larger breweries employing a com- 

 plete scientific staff and provided with the latest im- 

 provements. 



The present work is, we understand, intended to bring 

 before those connected with brewing a concise account 

 of the assistance which may be derived in the conduct of 

 their business from the use of the microscope. We are 

 of opinion that the authors have been unfortunate already 

 in the choice of their title, as one of the most conspicuous 

 results of modern scientific research in this direction is that 

 the use of the microscope alone is of comparatively little 

 value in the study of micro-organisms in general, whether 

 connected with fermentation or other processes. This in- 

 adequacy of microscopic study per se the authors in 

 various parts of their work indeed frankly admit. Modern 

 students of these low forms of life have, in fact, become 



more and more aware of the fallacious results yielded by 

 mere microscopical observation when unaccompanied and 

 uncontrolled by those processes of cultivation which have 

 been developed during the past ten years. Even the work 

 performed under the auspices of the masterly genius 

 and supreme experimental skill of Pasteur has had to be 

 revised and brought up to date by Hansen, with the aid 

 of the more recent methods of research. Now, although 

 the authors appear fully aware of the great change which 

 has taken place since the earlier work of Pasteur, Reess, 

 Fitz, and others, they have not sufficiently distinguished 

 between observations which rest upon the surest founda- 

 tion and fulfilling the most modern requirements, and 

 those which, though possibly correct, require repetition 

 and confirmation. 



The absence of sharp differentiation in this matter 

 cannot fail, we believe, to occasion much confusion in 

 the mind of the ordinary practical student who depends 

 upon text-books and manuals for his guidance and in- 

 formation, and it is, in our opinion, quite unnecessary 

 that he should be burdened with the microscopic de- 

 scriptions of the various forms of yeast given by the older 

 observers, who were almost certainly dealing with impure 

 cultures, but on the contrary he should rather devote his 

 whole attention to the charactersof such undoubtedly pure 

 forms of yeast as have been obtained by the most recent 

 methods. Moreover, unless the necessity of resorting to 

 these cultivation experiments for obtaining accurate in- 

 formation is duly impressed upon the student, he will 

 naturally be inclined to shirk these far more laborious 

 and difficult observations, and place undue reliance upon 

 microscopic features. 



These remarks apply, perhaps, with even greater force to 

 the manner in which the authors have dealt with the 

 schizomycetes ; in this part of the book we find much 

 space devoted to microscopic descriptions of bacteria ot 

 uncertain purity, whilst there is little or nothing said 

 about the methods by which these organisms can be 

 really identified, and their characters defined. We also 

 miss any adequate account of the staining-processes 

 which are so invaluable in obtaining a correct idea of the 

 microscopic forms and dimensions of bacteria. As an 

 instance of the unsatisfactory present condition of brew- 

 ing microscopy, we may quote the following sentence : 

 " Bact. lactis, as seen in beers, is generally in the form 

 of small rods, 2 to 3 /li in length, and sometimes in threads 

 containing from 2 to 5 individuals ; it is not certain, 

 I however, that this form is B. lactis." Thus, in respect of 

 I the bacterium which is perhaps of most consequence to 

 the brewer, as being "the most commonly occurring 

 , disease-organism encountered in the brewing process " 

 ' there is this absolute lack of all precise information. 



What may be called the more purely scientific part of 

 the work is succeeded by a chapter of " general rertiarks 

 on the brewing process," which, embodying as it does 

 some of the practical experience of the authors them- 

 selves, we would have gladly seen enlarged. 



The book, which is printed on excellent paper and 

 elegantly got up, is illustrated with a number of admir- 

 ably executed plates, many of the best of which are 

 original. 



A full index and glossary are appended. 



