678 



Gekzowitsch nan.eiy dissolved neutral red in ordinary Ringer fluid, the com- 

 position of which is not stated, and obtained at arterial transmission a "coloured'' 

 glomerulus filtrate; he does not say whether the colour was red or yellow orange. 

 HöBKR on tlie other hand injected neutral red into the back lymphsac, and on 

 examining the capsule microscopically he saw a " colourless' "^ glomerules filtrate. 



Probably the contradiction may be thus explained: Gerzowitsch uses "eine fur 

 den Frosch physiologische RiNGER-lösung". This must have been one, containing 

 0,02 '^0 NaHCO;, (see above p. 672) and this gives an acid i.e. a pink urine. 

 HöBER and Königsberg, however, worked under phyciological conditions, for normal 

 blood flowed through the frogs; only some vital colouring-matter had been 

 introduced into the back lymphsac. The glomerules filtrate was, just as with us, 

 colourless, but in its passage through the ducts it took up neutral red, which was 

 secreted by the epithelium of the tubuli. This would be in conformance with the 

 yellow colour of the urine, which we obtained when under practically physiological 

 conditions a suitable RiKQER-fluid was used. 



S Ü M M A R Y. 



1. If, the usual RiNüKR-solution containing 0.02 7o NaHCO,, passes 

 through the kidney, then it is found that of the 0.1 7o glucose 

 at most 0.03 " „ is retained (table II) in however favourable a manner 

 we may vary the Ca and K percentage. 



A considerable increase of the glucose retention may he attained 

 if the NaHCOt cone, of the transmission fluid is raised from 0.02 "/^ 

 to 0.090 7„. 



2. Experiments with neutralred teach that the cause of this phe- 

 nomenon is connected ivith the reaction of the transmission-fluid. 



If the alkalinity of the latter (i. e. its protective value) is so slight 

 that on being transmitted it is easily acidified, then the urine formed 

 gives an acid reaction (neutralred becomes pink) and little or no 

 glucose is retained. 



If, however, the NaHCO, cone, is raised to 0.090 7o then the 

 artificial urine remains alkaline (neutral red remains, yellow) and of 

 the ± 0.1 7o of glucose about 0.06 7ü ^^ retained. 



In order to obtain this favourale result, however, the Oa-coneen- 

 tration, the most effective cone, of which amounted hitherto to 

 CaCl, 6 aq. 0.015 »/„ (see tablet) must be raised to 0.024- 0.0307o 

 (table HI), but not higher. That the CaClj cone, should have to be 

 raised if the NaHCOg cone, is increased need not surprise us, since 

 an increase of the NaHCO, cone, impedes the dissociation of the 

 CaCl, and a sufticient concentration of ions of Ca in the transmission 

 fluid is of great importance. 



3. The kidney can retain even more than 0.06 7o ^f glucose if 



