SUGAR OF BLOOD. 111
amount of sugar may be present of which the ratio is higher than that
of a, " glucose. We were unable to test this by acid hydrolysis owing to
the small amount of filtrate in the final product. The further fact that
the polarimeter curve does not reach the original copper value tends to
support this hypothesis. It seems feasible to conclude that the direct
cause of diabetes is the lack or inactivation of the enzyme which causes
the conversion a, B glucose -+ y glucose.
1. A method is described for obtaining the sugar of blood in a con-
centrated solution free from proteins.
2. By means of this it is shown that the sugar in normal blood of man,
and of the ox, sheep, cat and rabbit, is an unstable form of glucose, with
an initial low rotatory power. It is suggested that the sugar is y glucose.
3. Glucose and fructose taken in large quantities per os cannot be
detected as such in the blood, their conversion into normal blood sugar
being very rapid.
4. Nervous influences alter the nature and quantity of the blood sugar.
5. The blood sugar of persons suffering from severe diabetes mellitus
is of an abnormal nature. It appears to be the a, f form of glucose.
6. An enzyme is postulated whereby the a, B equilibrium form of glu-
cose is converted into y glucose. This enzyme is absent from the blood.
7. The absence or inactivation of this enzyme is suggested as the
cause of diabetes.
We wish to express our grateful thanks to Mr J. J. Walsh, M.B.,
B.CLh., who has been ready at all times to perform the operations of
drawing blood from the normal subjects.
We are much indebted to Drs J. F. Gaskell, G. Graham, E. Lloyd
Jones and J. Aldren Wright, for obtaining for us blood from the
We wish to thank the following who kindly volunteered to allow
samples of blood to be taken from them: Messrs G. M. Dean, J. B. S.
Haldane, H. Mallinson, J. C. C. Poole, G. F. Taylor and H. L.
We especially wish to express our grateful thanks to Professor F. G.
Hopkins for his kindly criticism and help throughout the course of this
One of us (W. S.) wishes to thank the Scientific and Industrial
Research Board for a grant which was held during the latter period of