366 HERMAN O. MOSENTHAL 



will be necessary before the formula may be considered to be on a satis- 

 factory basis. It is probable that there is a good deal to be said for it, 

 but that it must be perfected in certain details before it can be accepted 

 as a standard clinical procedure; a similar stormy course has marked 

 the career of Ambard's coefficient for urea excretion. 



What other investigators have said concerning this equation may be 

 of interest. Wolferth notes that the normal sodium chlorid of the plasma 

 is 5.56 to 6.17 gm. per liter; in passive congestion it rises as high as 

 6.69 and in nephritis to 6.40, and that the renal threshold for chlorids is 

 raised in the two latter states; he finds that an elevated plasma chlorid 

 threshold is valuable evidence of the existence of a nephritis when cir- 

 culatory disturbances can be excluded. O'Hare believes that the index 

 of sodium chlorid excretion is of importance when the blood chlorids are 

 normal. Austin and Jonas, on the basis of experiments, came to the 

 conclusion that in normal animals the chlorid index holds true, but that in 

 nephritis (uranium) "there may be an alteration in the threshold, or 

 a disturbance in the degree of renal response to increments in the plasma 

 chlorids above the threshold. Because of these two variables, interpreta- 

 tion of the significance of alterations in the chlorid index of pathological 

 cases is complicated." 



Tests for Urea and Salt Excretion 



Monakow(a) (1911) following the ideas of French clinicians suggested 

 the addition of 10 gm. of salt and 20 gm. of urea to a patient's dietary. 

 O'Hare(a) (1916) described the procedure as follows: "The 'added urea 

 and salt test' has been carried out much as described by von Monakow. Our 

 patients have been placed on a diet containing 75 mg. of protein, 4 gm. of 

 sodium chlorid and 1,500 c.c. of water with caloric value of 2,000 to 2,200. 

 After the output of fluid, salt and nitrogen reaches an equilibrium on this 

 diet, on one day 10 gm. of additional salt is given, and several days later 

 the patient receives 20 gm. of urea. This order may be reversed. The 

 daily output of urine, salt and nitrogen is determined and charted." Then 

 O'Hare goes on to voice his impressions concerning these tests : "After 

 salt or nitrogen are added to the diet in normal individuals their excretion 

 after forty-eight hours return to its previous level. In the diseased kidney 

 this may not be the case. Sometimes the added salt or urea produces a 

 diuresis and this disturbs the elimination of both salt and nitrogen, the 

 increased water output carrying out with it more salt or nitrogen. Conse- 

 quently it is desirable to observe the effect of each added substance for 

 several days after it is given before introducing the other. Then it often 

 takes several days on the diet before salt, nitrogen and water excretion 

 reach an approximately constant rate of excretion. These several factors 

 render it desirable to prolong the added urea and salt test over a period 

 of ten or twelve days, and in some cases even longer. 



