50 SECTIONAL ADDRESSES, 
were encouraged to cherish the same intelligent sympathy with yeast- 
cells which they so willingly display towards domestic animals and 
silkworms, perhaps there would be fewer crazy dervishes to deny us the 
moderate use of honest malt-liquors and unsophisticated wines, fewer 
pitiable maniacs to complicate our social problems by habitual excess. 
Exactly how the cell accomplishes its great adventure remains a 
puzzle, but many parts of the machinery have already been recognised. 
Proceeding from the discovery of zymase (1897), with passing refer- 
ence to the support thus given by Buchner to Liebig’s view of fermenta- 
tion, Chapman emphasises the importance of contributions to the 
subject by Harden and W. J. Young, first in revealing the dual nature 
of zymase and the distinctive properties of its co-enzyme (1904), next 
in recognising the acceleration and total increase in fermentation 
produced by phosphates, consequent on the formation of a hexose- 
diphosphate (1908) : 
2CgHi205+ 2Naz2HPO, = 2C0.+ 2C,H,0 + CgHi904(PO.Naz)o+2H20. 
In this connection it will be remembered that a pentose-phosphate 
is common to the four nucleotides from which yeast nucleic acid is 
elaborated. The stimulating effect developed by phosphates would not 
be operative if the cell were not provided with an instrument for 
hydrolysing the hexose-diphosphate as produced, and this is believed 
by Harden to be supplied in the form of an enzyme, hexosephosphatase, 
the operation of which completes a cycle. As to the stages of dis- 
ruption which precede the appearance of alcohol and carbon dioxide, 
that marked by pyruvic acid is the one which is now most favoured. 
The transformation of pyruvic acid into acetaldehyde and carbon dioxide 
under the influence of a carboxylase, followed by the hydrogenation 
of aldehyde to alcohol, is a more acceptable course than any alternative 
based upon lactic acid. Moreover, Fernbach and Schoen (1920) have 
confirmed their previous demonstration (1914) of pyruvic acid formation 
by yeast during alcoholic fermentation. 
The strict definition of chemical tasks allotted to yeasts, moulds, and 
bacteria suggests an elaborate system of microbial trades-unionism. 
HE. C. Grey (1918) found that Bacillus coli communis will, in presence 
of calcium carbonate, completely ferment forty times its own weight 
of glucose in forty-eight hours, and later (1920) exhibited the threefold 
character of the changes involved which produce (1) lactic acid, 
(2) aleohol with acetic and succinic acids, (3) formic acid, carbon 
dioxide, and hydrogen. Still more recent extension of this inquiry by 
Grey and E. G. Young (1921) has shown that the course of such 
changes will depend on the previous experience of the microbe. When 
its immediate past history is anerobic, fermentation under anzrobic 
conditions yields very little or no lactic acid and greatly diminishes 
the production of succinic acid, whilst acetic acid appears in its place; 
admission of oxygen during fermentation increases the formation of 
lactic, acetic, and succinic acids, diminishes the formation of hydrogen, 
carbon dioxide, and formic acid, but leaves the quantity of alcohol 
unchanged. The well-known oxidising effect of Aspergillus niger has 
been shown by. J. N. Currie (1917) to proceed in three stages marked by 
