706 ACTION OF SALINE DIURETICS 



ureter. The object of the resistance was to slow down the flow 

 through the tubule, and so afford greater opportunity for ab- 

 sorption. He found that the urine from the obstructed as com- 

 pared with that from the free ureter contained less water and 

 chloride relatively to the phosphate, sulphate, urea, and pigment. 

 Filehne has been unable to confirm these results completely, and 

 believes that slight obstruction of one ureter may bring about differ- 

 ences in the urine from the two sides either by reducing the amount 

 of glomerular secretion or by affecting the secretion by the tubules 

 on that side. Nevertheless Cushny's experiments as they stand, 

 and others which will be considered later, suggest that the tubules 

 can absorb. But it must be remembered that in order to bear 

 this interpretation two assumptions are necessary. In the first 

 place, that the urine secreted by the two kidneys under normal 

 conditions is always the same. This has sometimes been found 

 to be the case, but in dogs and man at any rate not always so. 

 And in the second place, that moderate obstruction of a ureter 

 brings about the observed change in the urine by favouring 

 absorption from the tubule, and not by interfering with the blood 

 supply of the kidney nor by altering the secretory activity of renal 

 cells, nor by absorption in the ureter or pelvis of the kidney. It 

 has been found by experiment that a ureter pressure of 50 mm. Hg 

 reduces the venous outflow from the kidney by only 10 per cent. 

 It does not seem likely, therefore, that the ureter pressures used 

 by Cushny could have very materially interfered with the renal 

 circulation. Schwarz has maintained that a slight obstruction of 

 the ureter equal to 25 cm. of oil actually increases in dogs the flow 

 of urine, while the obstruction lasts, and has suggested that it 

 either interferes with absorption or stimulates secretion. And other 

 observers have obtained similar results. It is clear, therefore, 

 that the mode of action of partial obstruction of the ureter is still 

 a matter of controversy. 



We have seen that the injection of a salt solution alters both 

 the volume and composition of the blood, and might produce 

 diuresis either by stimulating secretory cells in accordance with 

 Heiden hail's view, or by changes in the renal circulation according 

 to Ludwig's view. But at present there is no evidence to 

 p'ove which of these is right. The different degrees of diuresis 

 produced by various crystalloids may be explained either by 

 differences in their secreto-motor action or by different degrees 



