1346 
position? And especially: Is the “combined” sugar kept back here? 
(We shall have to investigate whether the sugar is combined with 
protein, or phosphatides or cholesterin). This we have investigated 
most fully in the case of the liquid of the eye-chamber. The values 
for the sugar-percentage of this liquid, mentioned in the literature 
of the subject, did not help us much. We had to rely on our own 
researches. In the first place one nearly always finds indicated (as 
e.g. by OsBorNB')) that the sugar-percentage of the liquid of the 
eye-chamber is about equal to that of the blood. Nearly always 
however it is omitted to investigate blood and eye-chamber liquid 
simultaneously. This may be called the first requisite, on account 
of the important fluctuations of the sugar-percentage in the blood 
which are found even under physiological conditions; and, where 
this simultaneous investigation was performed, as in the very detailed 
communication of Ask’) of comparatively recent date concerning the 
eye-liquid, these researches have lost much of their significance in 
the light of our present state of knowledge. For, the liquid with 
which the humor aqueus must be compared, is not the total blood, 
but only the blood-plasm, the sugar-percentages of which are quite 
different. By investigations of most recent date, a.o. of one of us’), 
it has been established without doubt that in the case of a number 
of animals (in any case with man and the rabbit) the corpuscles 
are free from sugar. The value found when determining the sugar- 
percentage of the total blood, is therefore considerably lower than 
the actual concentration of sugar in the plasm. And, consequently, 
if one compares the sugar-percentage of the liquid of the eye-chamber 
with that of the total blood or with that of a blood-liquid the 
identity of which with blood-plasma is not entirely without doubt, 
one arrives at conclusions which are quite wrong. Serum obtained 
by the coagulation of blood, plasm obtained by blood-coagulating 
means (hirudin, oxalate) show a lower blood-sugar percentage than 
the plasm proper, because in these operations in an exceedingly 
short space of time part of the sugar disappears in the corpuscles, 
this being due to changed permeability-relations. In this way are 
to be explained Ask’s results (differing from ours) and his conclu- 
1) OSBORNE, l.c. 
*) Ask, Biochem. Zeitschr. 59, 1 and 35, 1914. 
8) S. vAN CREVELD and R. BRINKMAN: Proceedings of the Royal Acad. of 
Sciences Section of Dec. 17 1920. Further BRINKMAN and Miss vAN Dam: 
Arch. Internat. de Phys. XV, p. 105, 1919. In these articles elaborate 
bibliographies. 
