360 HERMAN O. MOSENTHAL 



PyC X 8.96 

 Wt. X Ur 2 



When values below 80 are noted the power of the kidney to excrete urea 

 is correspondingly diminished. 



The Coefficient of Austin, Stillman and Van Slyke. The "Urea-secre- 

 tory constant" of these authors is : 



For Normal Man : 



TT_ = = 7.5 -h3 



- BVVW 



D = Urea output (grams per 24 hour time unit) 

 B = Blood urea (grams per liter) 

 V= = Volume output (liters per 24 hour time unit) 

 W = Body weight (kilos) 



When values below the minimum normal of 4.5 are noted, the urea ex- 

 creting function is deficient. 



The urea-secretory constant, for normal persons is probably more nearly 

 correct than Ambard's formula. Its clinical worth remains to be tried out. 

 Judging from the successful application of Ambard's constant, it promises 

 to be of great importance. Austin, Stillman and Van Slyke believe that 

 their "urea-secretory constant" is an equation of definitely greater ac- 

 curacy than Ambard's. However, they do not consider their conclusions 

 a disproof of Ambard's work but rather an advance which has proceeded 

 along the path opened by his researches. A resume of their reasoning 

 is contained in the subsequent section. 



Facts Regarding Renal Function That Have Been 

 Developed by a Study of the Laws of Urea Excretion 



The Effect of Concentration of Urea in the Blood on the Quantity of 

 Urea Excreted by the Kidneys. It is a matter that admits of no doubt 

 that, other factors remaining constant, the amount of urea put out by the 

 kidneys in a given unit of time increases as the blood urea rises. The 

 exact proportion of these values to one another has been a matter of con- 

 siderable dispute. Ambard believed that the rate of urea excretion varied 

 proportionately to the square of urea in the blood. Subsequent investiga- 

 tors seem to agree that the ratio is a much more simple one, namely, that the 

 rate of urea excretion is directly proportional to the concentration of urea 

 in the blood (Addis, Barnett and Shevky, Addis and Watanabe(c), Aus- 

 tin, Stillman and Van Slyke, Marshall and Davis, Pepper and Austin (6) ). 

 According to them the equation would be : 

 urea in the blood 



rate of urea excretion 



= constant. 



