45^ PHYSIOLOGICAL CHEMISTRY 



Urine is now collected in one-hour samples. In patients with obstruction to the 

 flow of urine from the bladder the retention catheter is stoppered and the urine 

 drawn off at the end of each hour. Other patients may simply be allowed to urinate 

 at the hourly periods. 



To each hour sample of urine is added 25 per cent NaOH, drop by drop, until 

 the maximum intensity of color appears. This color will remain constant for an 

 indefinite period of time. Each sample is then placed hi a 1000 c.c. volumetric 

 flask and diluted to the mark with distilled water. 



Comparison is made in a Duboscq (Hellige or Sargent) colorimeter (see p. 486) 

 with a standard consisting of 3 mg. of phenolsulphonephthalein in 1000 c.c. of solu- 

 tion. The cylinder containing the standard may conveniently be placed at the 10 

 mm. mark. Since the volume of each urine sample is the same as that of the 

 standard, the percentage elimination of phenolsulphonephthalein in each may be 

 easily calculated as follows : 



Reading of Urine : Reading of Standard : : 100 : X. 



The amount of the drug eliminated normally is 40-60 per cent during 

 the first hour and 20-25 per cent during the second hour, or a total of 

 60-85 P er cen t f r two hours. The amount of the drug excreted has 

 been found to be independent of the quantity of urine obtained. 

 ,In case of delayed excretion the collection of hourly samples may be 

 continued until practically all of the drug has been recovered in the 

 urine. 



If it is desired to test the function of each kidney separately, 

 ureteral catheterization must be resorted to, the experiment other- 

 wise being performed as above described. 



The phenolsulphonephthalein test may be used to indicate the 

 amount of derangement in quantitative functional disturbance of the 

 kidneys, as in chronic interstitial and chronic parenchymatous neph- 

 ritis or uremia. 



McLean 1 has very recently suggested a method for studying kidney 

 function which is based upon the relationship between the urea con- 

 tent of the blood and the rate at which the urea is excreted by the 

 kidney. It gives similar values to the phenol-sulphonephthalein test. 

 It has an advantage in that it enables one to measure kidney function 

 by a study of an actual normal function of the organ, i.e., urea excre- 

 tion. The method, however, is more or less complex. 



1 McLean: Jour. Am. Med. Assn., 66., 415, 1916. 



