594 Dr. E. F. Armstrong. * [July 29, 
Change takes place in a similar manner in other media. If the glucose be 
dissolved in methylic alcohol containing hydrogen chloride, it undergoes 
etherification, each of the two glucoses being converted into the corresponding 
methylglucoside:* only one of these (the «-compound) is hydrolysed by 
maltase; the other (the §-compound) is hydrolysed by emulsin. The 
behaviour of these two glucosides is typical of that of glucosides generally, 
which are divisible into two groups, the « and the £, according as they are 
hydrolysed either by maltase or by emulsin. It is noteworthy that, apart 
from the sugars proper, in all cases in which the test can be applied, the 
natural glucosides have been found to belong to the @-group. 
The process by which a monose is converted into a biose must be regarded 
as precisely similar to that by which «-glucose and §-glucose are converted 
into the two methylglucosides: the behaviour of maltose, in fact, is such 
as to characterise it unquestionably as glucose-a-glucoside ; isomaltose is 
presumably the stereoisomeric glucose-S8-glucoside. 
When glucose undergoes condensation “uncontrolled,” it should give rise 
to both maltose and isomaltose, the proportions of which ultimately present 
in equilibrium would depend on their relative stability under the conditions 
operative at the time. But, inasmuch as hydrolysis under the influence of 
enzymes is an absolutely selective process, being so controlled that it takes 
place in one direction only, it might be supposed that synthesis under their 
influence would also be a controlled operation and that the tendency of the 
enzyme would be to reproduce the biose which it hydrolyses: apparently this 
point of view was present in Croft Hill’s mind and led him to suppose, at first, 
that maltose was the actual product; as a matter of fact, it is uncertain at 
present whether maltose is produced at all: it is certainly not the sole nor 
even the predominant product. 
The formation under the influence of the enzyme of a single biose, tsomeric 
with that which it hydrolyses, could be accounted for on the assumption that 
both are produced initially but tbat the one again undergoes hydrolysis as 
soon as it is formed, so that it all but disappears. If, however, it were shown 
that only the stereoisomeride of the biose hydrolysed is produced initially, it 
would be necessary to regard the synthetic activity of the enzyme as opposed 
to its hydrolytic activity. An explanation which in a measure unites both 
infers that the proportion in which these are present in equilibrium is a = 37 per cent., 
3 = 63 per cent. in a 10-per-cent. solution, and a = 40, 8 = 60 in a concentrated solution. 
Lowry (‘ Trans. Chem. Soc.,’ 1904, p. 1551), who bases his conclusions on determinations 
of solubility, takes the view that a solution of glucose contains a considerable proportion 
of glucose aldehydrol in addition to a- and B-glucose; but his argument cannot be 
regarded as a convincing one (‘ Comp. Jungius. Zeit. Phys. Chem.,’ 1905, p. 103). 
* KE. F. Armstrong and 8. L. Courtauld, ‘Proc. Physiol. Soc.,’ July, 1905. 
