1352 
of combined sugar of 0.09°/, whereas the mean difference between 
eye-chamber liquid and bloodplasm amounted to only 0.044 °/,. 
This figure is really low; for as an average in eight experiments 
we found a quantity of combined sugar of 0.075 °/, in ultra-filtrates 
(in vitro) of serum of our test-rabbits. | 
Now this difference between the processes in vitro and in vivo is 
not yet such that on the strength of this we should no longer regard 
the chamber-liquid as a kind of ultra-filtrate, but moreover we are 
inclined to think that this difference is not essential. For in com- 
paring the eye-chamber liquid and the plasm of the blood from an 
ear-vein we found an average difference of 0.044 °/,. But the blood 
which interacts with the eye-chamber liquid, will in no case be 
venous blood, but it will agree more with the composition of arterial 
blood. Now, as a consequence of the sugar-consumption of the 
various organs, the sugar-percentage of venous-blood will be lower 
than that of arterial blood; the magnitude of this difference will 
depend on the intensity of the sugar-metabolism of the particular 
organ. We may take for granted that this metabolism will be very 
slight in the case of the tissues (cornea, crystalline-lens) ete., which 
surround the eye-chamber, and also that the venous blood flowing 
from it, would differ very little from arterial blood, supposing we 
could investigate the former separately. This difference exists very 
distinctly when we compare blood taken simultaneously from the a. 
carotis and from the v. facialis posterior, the latter of which practi- 
cally corresponds to the blood from an ear-vein. In three experi- 
ments we found here differences of 0.09, 0.03 and 0.02, on the 
average therefore over 0.04°/,. If, therefore, we increase the sugar- 
percentage of the plasm from the ear-vein with this amount, the 
sugar-percentage of the chamber-liquid will correspond very well to 
what we should expect of an ultra-filtrate. 
As regards the second liquid investigated by us, the cerebro-spinal 
fluid, we can dispose only of a much smaller number of experi- 
ments. The statements in the literature of the subject made it pro- 
bable that here also we should find a sugar-percentage, lower and 
even considerably lower than that in the blood-plasm. Thus for 
example Fins and Myers’) state that with a number of patients the 
sugar-percentage of the cerebro-spinal liquid amounted to only 57°/, 
of that of the total blood. A similar statement we find in Weston’). 
For the reasons given before, this difference would become more 
') Proceedings Soc. Exp. Biol. 13, p. 126, 1916. 
*) Journ. of Med. Research. 35, p. 199. 
