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centrations, then the phenomenon of partial retention could not be 
explained by the idea of toleration and then a second explanation 
would per exclusionem be the correct one. 
2nd. This second explanation could be sought in the fact that 
the d-galactose exists in two modifications — an « and a B variety. 
In aqueous solutions these two varieties are in a state of equilibrium. 
Then it had to be accepted only that one of the two modifications 
was retained by the glomerular membrane, and the other not. 
1. Toleration of the kidneys for d-galactose. 
-To determine the toleration, the perfusion liquid was seasoned 
with different quantities of d-galactose lying between 0.05 °/, and 
0.25 °/,. The following table gives a survey of the results obtained. 
It will be clear without further explanation. Let it only be remarked 
that for the determination of the reduction the newest method of 
Bane (1918) was employed *). Hach time both kidneys of two frogs 
were perfused at the same time (see table U). 
What do these experiments teach us? 
Firstly: That none of the used galactose-solutions, whose con- 
centrations lie, as has been said, between 0.05 °/, and 0.25 °/, are 
completely retained by the kidneys. Secondly, that in all cases the 
retention amounted on an average to a half, independent of the 
concentration of the galactose-solution that was perfused. 
In both respects the galactose differs from the glucose; for, was 
there not found a ¢ota/ retention in the case of glucose when the 
solution was weaker than 0.05 °/,—0.08 °/, (individual differences)? 
In the case of galactose, on the contrary, there is no question of 
total retention. And, as regards the second point, in the case of 
galactose the toleration remains unchanged in spite of the increase 
in sugar concentration. Only when the concentration becomes as 
high as 0.25 °/, does the toleration diminish. Experiments with 
stronger concentrations were not made since the secretion of artificial 
urine then became too scanty. 
We still have at our disposal a number of former experiments 
in which the reduction was determined by the earlier method of 
Bane (1916), a part of which experiments have been published already. 
They are found together in the following table (II). As will be noticed 
the results are not as uniform as those of table I, but in any case 
they point in the same direction. 
1) Compare for this our previous article in these Proceedings. 
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