561 



3. Where the cause for the retention of glucose cannot be 

 ascribed to the size of its molecule, lue are bound to consider its 

 structure or conjiguraiion. There is the more occasion for doing this 

 because its isomerics, iaevulose and mannose, ai'e allowed to pass 

 altogether and galactose lo a large degree, as has been proved by 

 the experiments under discussion. 



4. Glucose therfore occupies a unique position among the mono- 

 saccharides in regard to the glomerulus membrane. In other words 

 the glomerulus membrane can distinguish glucose from the other 

 monosaccharides in a manner that revdnds of the relation of sugars 

 and ferments, in connection with which Emu, Fischku used the well- 

 known simile of a loch and key. 



In any case these experiments are again a neuj illustration oj 



the doctrine of stereoisometrics, but now not as has thus far been 



the case, through facts of chemical l)ut of physiological nature, 

 belonging to permeability. 



5. Not without theoretical and clinical importance seems the fact 

 that the capability for retention of glucose is not modified when 

 glucose and Iaevulose are simultaneously pi-eseut in the perfusion 

 liquid. The two sugai'S are simply separated as by a filter: the 

 glucose remains behind, the Iaevulose is passed. This also appears 

 to be the case with a mixture of lactose aTui glucose: the lactose 

 passes completely into the urine and the glucose is retained by 

 the glomerulus epithelium to the same degree as when there was 

 no lactose present. 



Groningen, September 1918. Physiological Laboratory. 



