679 



the NaHCO^ cone, is raised to 0.285 "/„ i.e. the cone, which corre- 

 sponds to the titrdtioji-alkalinity of frogs' .s-erum. But then again 

 more CaCl, must be added, at least 0.0307„ (table IV). 



4. It is remarkable that otherwise tl)an in the experiments in 

 which NaHCOg 0.09 7o was used (table III), now that the cone, is 

 0.285 7„, an addition of more CaCI, 6 aq than 0.030 7„, even of 

 much more, does not impair the retention (table IV). There are 

 reasons to assume tliat the most favourable cone, of ions of Ca brings 

 itself about automatically, when more CaCl, is added. The Ringer- 

 .9ol. in the hitter case, inhen^of ±0.1 7o of glucose upon an average 

 0.077o '^^(^'^ retained, ivas composed as f olloivs : NaC/ O.b "/„, NaHCO^ 

 0.285 7„, KCt 0.01 y„ CaCl, 6 ^.9. 'o.040 7„. 



5. If the tran.smis.non-Jiuid contained 0.05 7o of glucose, the 

 average concentration found in frogs' blood, then a sugarless urine 

 was obtained. This was even the case when the Ringek-soI. contained 



"0.06 7„ of glucose. 



6. This result seems important to us from a physiological-clinical 

 and from a general biological point of view ; from a physiological- 

 clinical point of view, because the retention of sugar by the kidney 

 has now been reduced to a question of permeability, so that the 

 supposition that glucose is bound by one of the serum substances 

 (sucre virtuel of Lepine) has become altogether unnecessary. Evidently 

 the chemical composition of the transmission-fluid determines the 

 state of the glomerulus epithelium, and consequently the permeability 

 of the membrane to sugar. The results are important from a general 

 biological point of view, because we have to deal here with a new 

 form of permeability, one in which cells under physiological condi- 

 tions, though easily permeable to salts, are impermeable to the likewise 

 crystalloid glucose, a form of permealnlity hitherto unknown and 

 very useful under the circumstances. ' 



Groningen, September 1917. Physiological Laboratory. 



49* 



