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VICTOR C. MYERS 



us a correct appreciation of the significance of the nitrogenous waste prod- 

 ucts which find their exit through the kidney. He pointed out that the 

 urea and creatinin stood in marked contrast to each other, since the former 

 was largely exogenous in origin, while the latter was almost entirely of 

 endogenous formation. Uric acid stood in somewhat of an intermediate 

 position, being about half endogenous and half exogenous under ordinary 

 conditions of diet. 



Satisfactory interpretations of variations in these non-protein nitrog- 

 enous constituents of the blood can scarcely be made without a knowl- 

 edge of their origin. The following brief statement may be made regard- 

 ing the formation of these compounds. Urea is formed largely in the 

 liver from the ammonia resulting from the deaminization of amino-acids 

 set free in digestion, but not of immediate use to the animal organism. 

 Uric acid originates as a result of the enzymatic transformation of the 

 amino- and oxypurins, in which various glands of the body participate. 

 Creatinin would appear to be formed in the muscle tissue from creatin. 



COMPARATIVE NITROGEN PARTITION OF URINE AND BLOOD IN PER CENT OF TOTAL NON- 

 PROTEIN NITROGEN 



It is of interest to compare the partition of the non-protein nitrog- 

 enous constituents in the blood with similar partition in the urine. (See 

 above.) Upon the ordinary mixed diet their approximate distribution 

 in the urine is 85 per cent urea N, 1.5 per cent uric acid N, 5 per cent cre- 

 atinin N, 4 per cent ammonia N and 4.5 per cent undetermined N. It is 

 quite natural to expect a somewhat similar relationship in the non-pro- 

 tein nitrogenous constituents of the blood, but the above table discloses 

 quite a different distribution. It will be noted that even in normal blood 

 the percentage of uric acid nitrogen is greater, if anything, than in the 

 urine, while the urea is definitely lower, the contrast with the uric acid in 

 the case of the creatinin and ammonia being even more marked. As Folin 

 and Denis have pointed out, the human kidney removes the creatinin 

 from the blood with remarkable ease and certainty, the completeness of the 

 creatinin excretion being exceeded only by the still more complete removal 

 of the ammonium salts. The striking difference between the ability to ex- 

 crete uric acid on the one hand, and urea and creatinin on the other, is 



