674 



frog's serum required 0.85 cc. of \, normal tartaric acid. The 

 titration alkalinity of frog's serum is, therefore equal to that of a 

 0.034-normal or a 0.285 '/^ NaHCO,-sol. We have, therefore, given 

 a NaHCOa cone, of 0.285 "/o ^o our transmission-fluid; to prevent 

 a resulting increase of osmotic piessure the NaCl cone, was lowered 

 to 0.5 V,. Now again it was obvious that the suitable CaClj 6 aq. 

 cone, would have to be raised again, as the cone, of the free ions 

 of Ca would again be repressed. 



The result will be found in Table IV. 



The maximum quantity of glucose begins to be retained at CaCl, 

 6 aq. 0.030 7o ; so this concentration is still somewhat higher than 

 if NaHCO, 0.9 '/, is used (then the cone, of CaCl, 6 aq. was, as 

 appears from Table III 0.024 7J. 



Table III shows that if the CaCI, 6 aq. rose to above 0.030 '/„, 

 the retention of glucose began to decrease. In Table IV, however, 

 when a higher cone, of NaHCOa was used, this was not the case; 

 even if the CaCl, 6 aq. cone, rises to 0.080 "/„, the glucose-retention 

 remains pretty well invariably high viz. an average of 0.07 7o- 0"^ 

 will be inclined to assume that this is due to the fact that in the 

 latter case the most favourable cone, of ions of Ca is brought about 

 automatically. 



Indeed when through the Ringer fluid containing 0.285 Vo of 

 NaHCOj and 0.080 "/„ of CaCl^ 6 aq., oxygen is led for some time, 

 a precipitate is formed of CaCO, '). The following physico-chemical 

 exposition will make matters clearer. 



[Ca ■■ ] [HCO/]' ^ [Ca-] [HCO.'] ^^ 



H.CO. ' [H-] 



The latter formula teaches that the concentration of the free ions 

 of Ca is only dependent on the cone, of the ions of H and those 

 of HCO, or also that the amount of Ca salt makes no difference, 

 when [ H ■ ] and \ HCOj ' ] are present in a certain suitable pro- 

 portion. Hence we see that there must be a buffer-system for ions 

 of Ca in this fluid. 



To sum up: in order to maintain a proper concentration of ions 

 of Ca it appears that not only tiie cone, of ions of HCO'j, but also 

 that of ions of H ' is of importance. A satisfactory regulation of the 

 cone, of ions of H is not so easy to arrive at in our circumstances, 

 where, if the kidnev is to function well, the fluid must be saturated 



1) We have invariably observed at the ultrafiltration of bloodserum that the 

 clear filtrate becomes troubled when shaken with air. owing to the foimation of 

 GaCOg, which was kept in solution by COo. 



