Physiology. — ‘Further Researches in connection with the permea- 
bility of the glomerular membrane to stereoisomeric sugars”. 
By Prof. H. J. HAMBURGER. 
(Communicated in the meeting of September 27, 1919). 
It has previously ') been shown that when a liquid, whose com- 
position is efficient, is passed through the bloodvessels of the kidneys, 
the grape sugar dissolved in the liquid is retained by the glomerular 
membrane. In this concern the concentration of the Ca-ions and 
H-ions play the principal part. This retention of glucose is very 
remarkable, seeing that other crystalloids like common salt, sulphates 
and phosphates are not retained by the glomerular membrane. The 
question then arose what the cause could be of this so efficient 
behaviour of glucose. Had it something to do with the size of the 
molecule? This supposition had to be dismissed when it appeared 
that lactose (C,,H,,0,,), which has a molecular weight almost twice 
as great, passed through completely, which was the case even with 
raffinose (C,,H,,0,,). Nothing else then remained but to accept that 
this phenomenon was to be ascribed to the particular configuration 
of the glucose molecule’). 
To test this conclusion by experiment other hexoses (C,H,,0,), 
isomeric with glucose, were examined. It appeared thereby that, in 
contrast with glucose, the fructose and mannose were allowed to 
pass through completely. The frog’s kidney isable thus to distinguish 
glucose from fructose and mannose. 
The cause thus indeed lay in the difference in chemical structure. 
Obviously the thought of the wellknown comparison with lock and 
key occurred: The key glucose thus does not fit in the lock glomerular 
membrane, while the keys fructose and mannose do. 
We now asked ourselves the question: will it perhaps be possible 
to point out a particular group of atoms in the glucose molecule 
which may be considered responsible for the retention? The attempt 
to answer this question forms the contents of this article. 
') HAMBURGER and BRINKMAN, These Proc. Meeting of January 27, 1917, Vol. 
XIX, NO. 8. | 
2) HAMBURGER and BRINKMAN, These Proc. Meeting of September 28, 1918, Vol. 
XXI, NO, 4. 
