Hippuric Acid 



407 



basis for the benzoate dosage that nearly the same amount is 

 obtained for any one individual as by the body surface plan. 

 This agrees with the results obtained by Austin, Stillman and 

 Van Slyke, 4 who found that the square root of the body weight 

 was more adequate than the body weight itself in their constant 

 for urea excretion. The correlation coefficient between the milli- 

 grams of hippuric acid excreted per square meter of body sur- 

 face and the volume of urine excreted on the same basis was 

 small, 0.13, negative and with a very high probable error, ±64 

 per cent., indicating that in general there it little relationship 

 between the excretion of hippuric acid and of water and that 

 there is a slight tendency for the kidney that shows the best 

 output of hippuric acid also to show the best concentrating abil- 

 ity. In the first group of 21 quite the reverse of this was true 

 namely that the greater volume of water that was excreted in a 

 test was accompanied by a greater relative amount of hippuric 

 acid. This was well shown by correlating the milligrams of hip- 

 puric acid excreted per kilo of body weight with the volume of 

 urine excreted on the same basis. The coefficient obtained was 

 0.42, positive, and with a probable error of ±28 per cent. A 

 comparison of some of the findings with the two groups are 

 shown in Table 1. 



It will be noted from Table 1 that 91 per cent, of the indi- 

 viduals of the group of 66 were able to excrete more than 85 

 percent, of hippuric acid theoretically obtainable from the in- 

 gested benzoate. Values lower than 80 per cent, in this test for 

 renal function should be regarded as indicating probable renal 

 insufficiency. 



Two normal individuals in a total of 89, given benzoate ac- 

 cording to the body surface plan gave evidence that glycine was 

 not furnished with sufficient rapidity for the synthesis and ex- 

 cretion of hippuric acid at the normal rate. The first, a healthy 

 medical student, gave on two occasions tests of 53 and 67 per 

 cent. He was thoroughly examined by Dr. George E. Fahr of 

 the Department of Medicine, who also determined his Van Slyke 4 

 urea excretion constant. This was within the normal limits. 

 The second student showed benzoate test figures of 69 on two 

 occasions and while not examined physically was apparently in 

 perfect health. Glycine in amount equivalent to the benzoate was 



4 Austin, J. H., Stillman, E., and Van Slyke, D. D., J. Biol. Chem., 1921, 

 xlvii,, 91. 



