1905. | Studies on Enzyme Action. 605 
The fact that the three hexoses which behave alike have one common 
enolic form (compare No. III of these Studies) is of utmost significance as an 
indication that the formation of the enol is the initial stage in the fermenta- 
tion of the hexose and that the breakdown of the molecule commences at 
the terminal carbon atom. This conclusion derives support from the fact 
that the methylglucosides, gluconic acid, ethylic gluconate and similar 
compounds—in which only the groups attached to the terminal carbon atom 
differ from those in glucose—are unfermentable. 
The formation of the enol cannot take place without the carbon-oxygen 
ring undergoing rupture. It is in this direction perhaps that an explanation 
will be found of the fact that the bioses cannot be fermented directly or 
without previously undergoing resolution into the simpler hexoses. To judge 
from the behaviour of compounds such as the methylglucosides, it is probable 
that the conversion of the glucose into a glucoside involves an increase in 
the stability of the ring structure: perhaps, therefore, the ring structure in 
the bioses is of sufficient stability to remain unruptured in solution; in other 
words, it is possible that, whereas a solution of glucose contains the three 
isodynamic forms of the compound, viz., a-glucose, 8-glucose and the corre- 
sponding enol—the last being present probably only in small proportion 
and as the hydrated compound or aldehydrol—a solution of a biose such as 
maltose contains only the two isodynamic forms corresponding to the two 
elucoses. 
