Scientific Proceedings (67). 



the same time or several days later, the elimination of these dyes 

 may be partly or entirely inhibited. In some experiments, 

 permanent arrest of the passage of these substances was caused by 

 the administration of chenopodium. 



98 (1030) 



An index of urea excretion. 



By Franklin C. McLean. 



[From the Hospital of the Rockefeller Institute for Medical Research, 



New York.] 



Ambard and Weill have expressed the relationship between the 

 concentration of urea in the blood and the rate of its excretion by 

 means of a formula known as Ambard's coefficient, 1 the accuracy 

 of which has been confirmed on a number of normal individuals 

 by the author and Selling. 2 We now use the Ambard laws in a 

 new formula, which expresses the ability of the kidney to excrete 

 urea in percentage of the normal efficiency. 



/(Index) = mxUr2 . 



I = index of urea excretion (100 = average normal, 80-150 



maximum normal variation). 

 D = grams urea excreted per twenty-four hours. 

 C = grams urea per liter of urine. 

 Ur = grams urea per liter blood. 

 Wt = weight of individual in kilos. 



The index measures directly one of the more important func- 

 tions of the kidney and has yielded valuable data in the study of 

 various conditions associated with impaired elimination. For the 

 calculation a special slide rule has been devised, which enables 

 one to make the necessary calculation without effort in a few 

 seconds. 



1 Ambard, Compt. rend. Soc. de biol., 1910, Dec. 3, p. 506. 

 1 McLean and Selling, Jour. Biol. Chem., 1914, XIX, 31. 



