358 
remembered no trace is retained by the kidney. But it appeared 
through stalagmometric experiments (J. TrAUBE) and through experi- 
ments where the height of the meniscus through capillary action was 
made use of, that there existed no difference in the surface tensions 
of the two sugars. Neither did the viscosities of the two sugars show 
any difference. 
We now turned to the adsorption; would the glomerular mem- 
brane perhaps adsorb glucose, and, on the other hand, not fructose ? 
As a matter of fact we would not have busied ourselves with 
these experiments had not O. Conny ') conducted similar ones. 
For, supposing that the glomerular membrane adsorbed d-glucose, 
but no laevulose, then it would be extremely difficult to explain 
the different behaviour of the living kidney toward these two sugars 
through this. But, in any case, this would at least be an indication 
in the direction in which the explanation of the facts has to be 
sought. In addition to this there remains the fact that COHNHEIM 
could indeed notice differences in the adsorptive power of the kidney 
substance of warm blooded animals towards glucose and laevulose. 
However there are several grounds on which this conclusion of 
ConnHEmM can be doubted. | shall communicate about this in another 
place and point out through the medium of experiments conducted 
with frogs’ kidneys, that the methods pursued by this investigator 
viz., to experiment with mashed kidney substance, to determine the 
adsorptive power of the kidney for sugars, must lead to results 
which cannot be relied upon. 
Summary and Conclusion. 
To investigate whether a particular group of atoms can be held 
responsible for the retention of glucose by the kidney, a number 
of stereoisomeric hexoses and pentoses were examined with regard 
to their behaviour towards the kidneys. 
C—OH 
| 
The hypothesis that the group eon causes the retention 
cannot be true seeing that l-arabinose and l-mannose which have 
this group pass completely through the kidney, while the d-galactose, 
the l-xylose and the d-ribose in which this group is also present 
are partly retained, it is true, but still the other part is allowed to 
pass through (partial retention that is). 
In keeping with the hypothesis the sugars whose first 
1) Connnem: Zeilschr. f. Physiol. Chemie, 84, p. 451. 
