52 Paul Fourman and Patricia M. Leeson 



low. The ratio of urine to plasma osmolalities, which can 

 normally rise to about 4 with water deprivation, was 3-7 in 

 Albert and 3-3 in Ivor. The deprivation of water was associ- 



Table II 



Effects of depriving the two patients of water for 19 hours 



Changes in urine and plasma 

 Maximum urine concentration (m-osm/1.) 

 Flow at maximum concentration (ml./min.) 

 [Na] ((jL-equiv./ml. of urine) 

 Plasma (m-osm./l.) 

 Change in plasma ([Na] m-equiv./l.) 



ated with a great reduction in the renal excretion of sodium, 

 and the increases in the plasma [Na] were unexpectedly 

 large. They were not maintained however, for the plasma 

 [Na] had returned to the original levels after 48 hours. 



Effect of water 



The effect of a water load was adequately tested only in 

 Albert, who on 15th July received one litre of water in 30 

 minutes, by stomach tube. He excreted all of this water in 

 less than three hours, achieving a diuresis of 7-3 ml./min., 

 with an osmolal concentration of 54 m-osm./L, and a sodium 

 concentration of 4 m-equiv./l. These low concentrations are 

 similar to the minimum values obtained in normal persons 

 (Schoen, 1957). The values for the plasma sodium before and 

 after the test were 115 and 112 m-equiv./l. Remarkably low 

 osmolal concentrations were found twice in the 24-hour 

 collections of urine from Albert. The values, 153 and 168 

 m-osm./L, were lower than in the plasma, in spite of the fact 

 that at these times the plasma [Na] was exceptionally low, 

 104 m-equiv./l.; these values were obtained on the days 

 immediately following administration of pitressin (see below). 



We did not find any very low urinary concentrations in 

 eight 24-hour collections from Ivor that were tested. In one 

 specimen an osinolal concentration of 245 m-osm./l. was the 

 same as that of the plasma taken at that time. 



