URETER PRESSURE. 179 



or other condition will bring about a similar fall in ureter-pressure, only 

 that here the exact parallelism may be altered in two directions, firstly 

 reabsorption of fluid out of the tubules more rapidly than produced by 

 the kidney at the lowered blood-pressure, or secondly and oppositely the 

 kidney blood vessels remaining widely dilated and the kidney capillary 

 pressure proportionately high, the pressure in the ureter would be 

 insufficient to dilate the tubules and hence to allow a fall proportional 

 to the fall in the general blood-pressure. I have no doubt that this 

 is the only possible explanation of the remarkable result reported by 

 "Gottlieb and Magnus as they seem to have fulfilled all the necessary 

 theoretical conditions. In their experiment a rabbit received a con- 

 tinuous injection intravenously of normal saline, the blood and ureter- 

 pressures were noted while a fall in general blood-pressure was brought 

 about by injections of chloral. Reabsorption from the tubules would 

 here be slight if not indeed quite absent, and the renal vessels would be 

 widely dilated, hence it is not surprising that in the rabbit's last minute 

 the ureter-pressure was read at 14 mm. Hg, that of the blood in the 

 carotid only at 13 mm. The ureter-pressure was insufficient to press the 

 fluid in the connections back into the kidney. Though I have worked in 

 several experiments with very similar conditions I have never seen such 

 a result, and I think that this is due to the care taken to avoid error by 

 opening the ureter manometer connections on inducting changes in the 

 circulatory conditions, which Gottlieb and Magnus did not do. Con- 

 sequently, too, no absolute value should be placed on measurements of 

 ureter-pressure as it is in large part but a function of the blood-pressure 

 in the kidney, and the blood -pressure should always be given when the 

 ureter-pressure is used in experimentation. 



The second factor is the constitution of the plasma. Starling 

 measured the osmotic pressure value of the proteid constituents of the 

 plasma and found it to be about 25 30 mm. Hg. He pointed out that 

 with a normally constituted plasma one did not find a secretion of urine 

 with a lower blood-pressure than about 35 mm. Hg, nor under like 

 conditions could one obtain a ureter-pressure which was not lower than 

 the blood-pressure by at least this amount. Without diuretics in rabbits 

 the minimum difference between blood and ureter-pressure in my ex- 

 periments was 66 mm. Hg, with caffeine 46 50, hypertonic salts 45 ; 

 in dogs 60 70 mm., with diuretin or caffeine 55 65, with hypertonic 

 salts (10 c.c. of a 25 / solution of sodium sulphate) 47 mm. Hg. As 

 my experiments were performed in warm weather it was very hard to 

 obtain maximal activity in response to diuretics, and hence in part the 



