THE SECRETION OF URINE 1283 



output of this salt. The same thing holds for sugar. If an excess of 

 free uncombined sugar be present in the blood, either in consequence 

 of intravenous injection of this substance or as a result of previous 

 extirpation of the pancreas, any form of diuresis will increase the rate 

 at which it is turned out by the kidneys. Lowi concludes that phos- 

 phates, which must be present in minimal quantities in the glomerular 

 transudate, are for the most part secreted by the activity of the cells 

 of the convoluted tubules. Under abnormal conditions, e.g. as after 

 administration of phloridzin, the cells of the kidneys can be excited to 

 a similar activity with regard to sugar. After phloridzin injection the 

 urine contains considerable quantities of sugar, but the rate at which 

 the sugar is secreted is not affected in any way by raising the rate of 

 urinary secretion, e.g. by the injection of such substances as sodium 

 sulphate, which increases the rapidity of the glomerular process of 

 transudation. 



ABSORPTION BY THE RENAL TUBULES. The experiments 

 of Ribbert, mentioned above, in which removal of the medullary 

 portion of the kidney led to the formation of an increased quan- 

 tity of a more watery urine, points to the possession by the 

 tubules of a power of absorbing water. We have other evidence 

 that this power of resorption is not confined to water, but may affect 

 also the dissolved constituents of the glomerular transudate. It was 

 pointed out by Meyer that, if two salts, such as sodium sulphate and 

 sodium chloride, were present at the same time in the glomerular 

 transudate, any process of resorption should affect chiefly the more 

 diffusible salt, namely, sodium chloride. Such a differential resorption 

 would account for the much greater diuretic power of sodium sulphate 

 a 3 compared with sodium chloride. In certain experiments Cushny 

 produced a diuresis by the injection of equal parts of equivalent 

 NaCl and Na 2 S0 4 solutions into the veins of a rabbit. An increased flow 

 of urine was produced which lasted two hours and a half. The chlorides 

 of the urine rose with the diuresis and reached their maximum at the 

 height of the urinary flow. They then sank, and in some experiments 

 had practically disappeared from the urine towards the end of the 

 observation. The concentration of the sulphates, however, continued 

 to rise in the urine to the end of the experiment. Thus in the first of 

 two identical experiments, when the rabbit was killed at the height 

 of the diuresis, the serum contained 0-547 per cent, chlorine and 0-259 

 per cent, sulphate, while the urine contained 0-372 per cent, chlorine 

 and 0-546 per cent, sulphate. In the second, in which the rabbit was 

 killed when the rate of the urinary flow had considerably diminished, 

 the serum contained 0-493 per cent, chlorine and 0-191 per cent, 

 sulphate, while the urine contained -094 per cent, chlorine and 2-0 

 per cent, sulphate. These results are illustrated in Fig. 534. 



