702 ACTION OF SALINE DIURETICS 



The interpretation of the results of total obstruction of the 

 ureter is further complicated by the fact that the blood flow 

 through the kidney is at the same time interfered with. This 

 may well account for the observed oedema of the perinephric tissues. 

 It has been supposed that the distension of the renal tubules 

 causes them to press upon the venules in the kidney. Whatever 

 the explanation is, experiments have shown that when the ureter 

 pressure is raised to 100 mm. Hg the kidney becomes dark in 

 colour, the oncometer shows a great expansion of the kidney 

 volume, and the outflow from the renal vein and pressure in its 

 interior are considerably reduced. This interference with the 

 blood flow through the kidney might affect filtration by the 

 glomeruli or excretion and absorption by the tubules. In fact, 

 we can only conclude that experiments dealing with the total 

 occlusion of the ureter throw no light at present on the mode of 

 action of the glomerulus or tubule. 



Action of Saline Diuretics. In no part of the subject dealing 

 with the secretion of urine has more work been done recently 

 than upon the action of the saline diuretics. They include all 

 crystalloids which can be injected intravenously in large quantities, 

 such as NaCl, Na 2 HPO, Na 2 S0 4 , urea, dextrose, &c., and therefore 

 correspond to Heidenhain's second class of lymphagogues. 



It was known that the injection of one of these substances 

 would cause a secretion after the flow of urine had been stopped 

 by section of the spinal cord, and that at the time of the secretion 

 the arterial blood pressure was raised. But Heidenhain con- 

 sidered that the action of these substances could not be accounted 

 for by a vascular change, because their injection might under 

 normal circumstances increase the secretion of urine without at the 

 same time altering the aortic blood pressure. He therefore con- 

 sidered that these substances acted as specific stimulants to the 

 secretory activity of the renal cells. 



It was shown, however, that the diuretic effect of different 

 solutions corresponded roughly to their osmotic pressure, and 

 further that their injection produced hydrsemic plethora. The 

 vascular changes accompanying hydraemic plethora have been 

 shown by Starling to consist of a very slight rise in aortic pressure, 

 a dilatation of the visceral vessels, a general rise in the venous 

 and capillary pressures, and an increased rapidity of blood flow. 

 Starling investigated the action of dextrose on the renal circula- 



