SUGAR OF BLOOD. 105
it would occur with great rapidity. Our negative results are in agreement
with the conclusion of Cooper and Walker(lo), who state that no such
enzyme is present in the blood.
The only experiments which we can find in which the sugar of the
blood has been investigated as regards its copper reducing power and its
polarimetric value are those of Oppler(ll). We attribute the little or
no difference he found in the two values to the long time required to
obtain a concentrated protein free solution by the method he employed,
and to the sugar being in aqueous solution throughout-conditions which
would allow the sugar to be converted into the a, 1 equilibrium form.
Experiments with human blood.
In view of the results obtained from the blood of animals, it became
of interest to determine the condition of the sugar circulating in the
blood of man. The blood was drawn from an arm vein by means of a
hiypodermic needle and syringe into a known amount of 1 p.c. ammonium
oxalate solution in a measuring cylinder, with constant shaking to
prevent clotting of the blood. The precipitation was then carried out at
once. These operations were carried out at Addenbrooke's Hospital,
except in two diabetic cases. At the same time a sample of blood was
taken on which a quantitative estimation was effected by Bang's old
method.
In normal persons with one exception the first polarimeter reading
on the final filtrate showed that sugar in the blood had a specific rotation
which was considerably below that of a, B glucose as deduced from the
copper value. This is entirely comparable with our experiments with the
blood of animals. The curves approach the copper value in a similar
fashion; in some cases this value was not reached, and some subsidiary
action was evidently occurring. In Fig. 1 are shown the curves of the
polarimetric readings of three normal individuals. It will be seen that
in each case they start below their respective copper values. These are
calculated for glucose. The curve of H.M. did not quite reach its end point
in four days. Both of the others were in equilibrium on the third day.
H e w i t t and P ry d e's experiments (s) suggest that solutions of glucose
and fructose in contact with the mucous membrane of the intestine are
converted into y glucose; presumably they enter the blood in this form;
to test this it seemed desirable to determine whether any alteration in
the nature of the blood sugar could be brought about by ingestion of
considerable quantities of these sugars. While the experiments with
glucose might be open to doubt on the grounds of a small difference in