Renal Function in Acute Nephritis. 87 



In another case the function was higher when the kidney- 

 excreted at a rate of 7 gm. than when it excreted 13 gm., with the 

 blood concentration unchanged for the two determinations. 



Date. 



Blood Urea. 



Urine Cone. 



Rate D. 



Index. 



June 21 



O.29 



9.4 



7.0 



32 



July 12 



O.28 



1-7 



13-4 



27 



Other facts could be adduced to demonstrate that Ambard's 

 formulae are untenable as physiological laws. Whatever clinical 

 value is possessed by the index is due to the fact that a patho- 

 logical kidney so frequently retains urea and is unable either to 

 concentrate normally or to excrete the usual amount of urea — all 

 factors tending to decrease renal function as expressed by the index. 



Numerous estimations of McLean's chloride index were made 

 on these cases but in no case was the rate of excretion clearly 

 dependent upon the concentration of chlorides in the plasma. 

 In general the latter remained fairly constant, as soon as equilib- 

 rium was established after diuresis, while the urinary output was 

 proportional to the daily intake. With identical plasma chlorides 

 the rate of excretion showed the widest variations under different 

 dietary regimes. For example, with a constant plasma concen- 

 tration, one case excreted at a rate of 0.6 gm. on a salt-poor diet 

 and at 13.6 gm. when 4 gm. of salt were added daily to the diet. 

 Other cases showed the same picture, a picture difficult to ascribe 

 to changes in the course of the diseases. The reaction to a 

 single administration of 7 gm. of salt was interesting. There was 

 a rise of 0.2 gm. per liter in the plasma concentration with no 

 change in the rate of excretion; but forty-eight hours later the 

 rate of excretion had increased seven times, although the plasma 

 was unchanged. 



I wish to call your attention to a pertinent experiment upon 

 a normal individual. Table I is self-explanatory. There is a 

 marked increase in the threshold with the assumption of a salt- 

 poor diet; in fact, few nephritics show so high a threshold. One 

 of the most striking things is the actual increase in plasma con- 

 centration coincident with a decrease in urinary salt output. 

 This experiment I have been unable to repeat (for lack of time) , 

 but if confirmed it is sufficient evidence that Ambard's laws of 



