January i8, 19 12] 



NATURE 



o^o 



power of yeast, as Pasteur supposed, actually tended to 

 stimulate it. 



Undoubtedly the most striking advance in connection 

 with fermentation is Buchner's famous discovery that the 

 direct cause of the fermentative power of yeast is an 

 enzyme present in the cell. This at once destroyed all 

 theories connecting fermentative power with the vital 

 activity of the cell. The enzyme has been termed zymase, 

 and its behaviour, which in many respects differs from that 

 of other enzymes, has been studied very fully both by 

 Buchner himself and also by Harden, whose results are 

 of a very remarkable character. 



When yeast juice, which contains active zymase, is 

 filtered through a Chamberland gelatine filter, it is 

 separated into two portions, one of which remains on the 

 filter, whilst the other passes through. Apart, neither por- 

 tion has any fermentative power ; when united they ferment 

 sugar. The filtrate still retains the power of activating 

 the residue after it has been boiled ; it has been named 

 the co-enzyme. The part retained on the filter is destroyed 

 by boiling ; it is considered to be the enzyme. 



Further experiments showed that dilute solutions of 

 sodium or potassium phosphate have a marked stimulating 

 effect on the activity of zymase, and proof has been 

 afforded that a compound of sugar and phosphoric acid is 

 formed when such addition is made. At the same time, 

 a part of the sugar is decomposed to alcohol and carbon 

 dioxide. An enzyme, appropriately named hexosephos- 

 phatase, is present in yeast juice, and serves to break down 

 the compound of sugar and phosphate into its components. 



Such facts as these have introduced altogether new con- 

 ceptions into the knowledge of enzymes. 



Without going into greater detail in so complex a sub- 

 ject. Dr. Harden 's explanation of the fermentation process 

 may be summed up somewhat as follows. 



Enzyme and co-enzyme act in unison on a mixture of 

 hexose sugar and phosphate ; one half of the sugar is 

 decomposed into alcohol and carbon dioxide, and the other 

 half combines with the phosphate, forming hexosephos- 

 phate. The phosphate is thus for the time being put out 

 of action, but the hexosephosphatase enzyme comes into 

 work and resolves it into free phosphate and free sugar, 

 when the cycle of changes begins anew. The speed of 

 fermentation is regulated by the activity of the hexose- 

 phosphatase. Dr. Harden has calculated that with 

 ordinary brewer's yeast at 25° C. the whole of the phos- 

 phorus of its cell goes through this cycle twice in every 

 five minutes ! 



It is well known that, besides ordinary ethyl alcohol, 

 small quantities of other higher alcohols are formed during 

 fermentation, particularly under the working conditions of 

 a distillery. The explanation of the formation of these 

 " fusel oil " constituents has been long outstanding, but 

 quite recently Ehrlich has proved beyond doubt that they 

 arise from the action of yeast on the amino-acids ordinarily 

 present in fermentable liquors. These alcohols are physio- 

 logically of great importance as stimulants and excitants 

 of protoplasmic activity. Their presence, even in the 

 minutest quantity, has considerable bearing on questions 

 of flavour, so that technically the proper understanding of 

 their mode of formation is a matter of great importance. 

 Khrlich's researches have gone far in this direction, and 

 their application in practice is bound to lead to valuable 

 results. It is not improbable that many of the subtle 

 flavouring materials met with in plants may originate 

 from amino-acids in the same manner. 



Much has been done in studying the influence of traces 

 of other substances on yeast, since the final character 

 of the beer depends to a large extent on the fermentation 

 being normal. As showing how sensitive the living cell is 

 to stimulus, the effect of zinc cm iln' i^rowth of the mould 

 fungus, AsprrfiiUus niger, ni.i\ In rited. Almost incon- 

 ceivably small amounts of this 1 liiiitnl — a dilution of i part 

 in 50 millions — are capable of exercising a noticeable effect 

 in favouring growth. Copper in like dilution is known 

 to have a poisonous effect on bacteria, and it is evident 

 that the brewer must use the greatest care in the selection 

 of his vessels. 



In addition to the thirteen elements which are generally 

 stated to be essential to plant life, many others are found 

 in plants in very small quantities. The tendency has been, 

 for the most part, to regard these as accidintally acquired, 



NO. 2203, VOL. 88] 



and not essential. Latterly the point of view is changing,, 

 and there is evidence that some at least of the elements 

 present in minimal quantities play a very important part. 



Sufficient has been said to indicate how closely science 

 and brewing arc connected, and how many problems still 

 await solution. 



EDUCATIONAL CONFERENCES 

 CONSIDERED IN RELATION TO SCIENCE IN 

 PUBLIC SCHOOLS. 

 1. 

 'JpHE end of the second week in January marks the close 

 of a series of conferences which are annually attended 

 by teachers. The majority of these conferences are con- 

 cerned, in the main, with topics which have only a remote 

 connection with the subjects usually connoted by 

 " science." An exception to this statement must, of 

 course, be made in the case of the proceedings of the 

 Association of Science Masters in Public Schools, which 

 have a strong and beneficial influence on the early training 

 of men who may be expected to take leading positions, 

 not only in the university, but in the country generally. 

 It is owing in part to the realisation of this influence, in 

 part to the sensitiveness and ready response to stimuli of 

 the audience, in part to good management of the society, 

 that the association has been able to secure, year by year, 

 an address from a man of real eminence, and this time 

 special importance was given to the meeting by the fact 

 that Sir Joseph Thomson had accepted the office of presi- 

 dent. His address is reproduced elsewhere in this journal : 

 we may here testify to the obvious enjoyment which il> 

 delivery gave to the audience, and ask the serious atten- 

 tion of headmasters to the weighty remarks concerning 

 neglect of the German language. 



The first paper was contributed by Mr. M. D. Hill 

 (Eton), who has been led by his own experience to doubt 

 the necessity, or even the wisdom, of previous training in 

 chemistry and physics for young biologists. In the dis- 

 cussion the weight of opinion was clearly in favour of 

 insistence on such training. Mr. E. I. Lewis (Oundle), in 

 the next paper, argued that plant biology should be taught 

 in every secondary school. It was a subject the interest 

 and value of which increased throughout life. For junior 

 pupils the subject of plant life affords a preparatory study 

 full of suggestion lor tlu after-study of chemistry, and it 

 does not demand a special technical knowledge on the 

 part of the teacher. The work can consist almost entirely 

 of observation and experiment in the class-room and out 

 of doors ; it abounds in examples of comparative method. 

 Another paper dealing with the sequence of subjects was 

 read by Mr. C. E. Ashford (Royal Naval College, Dart- 

 mouth), who discussed the place of electrostatics in a school 

 course of electricity. Mr. .Ashford began by excluding from 

 the discussion the case of those students of eighteen years 

 and above who are studying as " science specialists " with 

 good mathematical equipment, and invited consideration 

 of the average boys about fifteen years old. He supported 

 the theory which (!■ pi > < it.s teaching subjects for their 

 artificial " disciplii • , ' md attaches importance to the 

 value of the " content " or subject-matter. On these 

 grounds, and by reason of the great interest evoked in 

 the inquiring mind of boyhood by the everyday phenomena 

 of current electricity witnessed in modern life, it seemed 

 good to begin with the effects of the current, and to post- 

 pone electrostatics until some idea of Ohm's law had been 

 obtained. One unfortunate result of insistence on pre- 

 liminary electrostatics had been unduly to postpone the 

 study of electricity in those practical applications which 

 appeal to the ordinary boy. 



Mr. Ashford had been convinced by his experience at 

 Harrow of the soundness of these propositions, and he pro- 

 ceeded to sketch a plan of teaching in accordance there- 

 with. He showed by demonstrations with the current from 

 the lighting supply, and with commercial instruments, how 

 readily electrostatics could be made to follow the current 

 work, and directed attention to the fact that success did 

 not depend on the weather. Prof. Worthington criticised 

 the details of Mr. .Ashford's scheme, and advocated the 

 older plan of taking electrostatics first. Mr. Sanderson, 

 on the contrary, regarded the teaching of electrostatics t» 



