THE IMPORTANCE OF LIME. 195 



of opinion that this " ferment " was nothing more than a proteid 

 body in a state of incipient decomposition. EvenT. A. QUEVENNE 

 (1.), who did not dispute that yeast possesses the characteristics 

 of a living organism, regarded the ash of same as something 

 quite immaterial an accidental impurity. 



Since, as already mentioned, the proteids also contain ash, it 

 was not possible to affirm the necessity of mineral foodstuffs for 

 the development of yeast, until a nutrient medium had been 

 discovered in which the nitrogenous food constituents were present 

 in a state of combination free from ash. This was first success- 

 fully accomplished by PASTEUR (VII.), who proposed to employ the 

 readily procurable ash from beer yeast for the purposes of 

 artificial culture in nutrient solutions in the laboratory. 



The further problem of the number and character of the in- 

 dispensable inorganic elements was not attacked by Pasteur, the 

 first to do this being ADOLF MEYEK (I. and V.), who ascertained, 

 by numerous culture experiments, that the mineral foodstuffs 

 indispensable and sufficient for the development of yeast are 

 potassium, magnesium, iron, phosphorus and sulphur. 



The resulting indirect assumption that lime is unessential 

 conflicts with the practical experience, of brewers especially, that 

 worts and mashes poor in lime give a very defective fermentation. 

 In view of this circumstance, the preceding sentence requires 

 modification in so far that, though lime may not be essential to 

 the actual growth of yeast, it forms an indispensable adjunct or 

 stimulant when the fermentative power of the yeast is concerned. 

 The part played by lime in this connection is still unknown, and 

 its investigation would be a very thankworthy task. Possibly it 

 combines with and nullifies the action of the poisonous oxalic 

 acid, which was shown by C. WEHMER (V.) to be a common and 

 important final product of the metabolism of numerous fungi, in- 

 cluding Aspergillus glaucus, A. niger, Penicillium glaucum, Mucor 

 mucedo, Rhizopus nigricans, Phycomyces nitens, Peziza Fucka- 

 liana, &c. In the case of these fungi, the acid can probably be 

 rendered innocuous by the magnesium present, though the larger 

 quantities produced by the far greater fermentative activity and 

 substantive transformations resulting in the case of yeast, cannot 

 be properly dealt with by that base alone. A more careful 

 examination (which does not seem to have been undertaken as 

 yet) of the gradual increase in formation of oxalic acid during 

 the fermentation of beer wort, and the determination of the 

 nature of the base, or bases, with which this acid is combined, 

 will, it is hoped, bring us a step nearer to solving the problem 

 of the importance of lime in connection with yeast. 



As the result of wide experience, brewers are agreed that 

 yeast which has been grown in worts poor in lime quickly degene- 

 rates, and in particular is incapable of producing " break " in the 

 wort. This defect is frequently experienced in breweries com- 



