426 JOSEPH H. PRATT 



of combined uric acid was about fifty per cent of the total uric acid. The 

 freeing of the uric acid was accomplished by Benedict's procedure of boil- 

 ing the protein-free filtrate with hydrochloric acid. 



Bass(c), and later Schiller and Wiener (a), found in human blood 

 purin compounds, either nucleotids or nucleosids, which on hydrolysis 

 yielded adenin. They are present in the serum, but especially in the red 

 blood corpuscles. The whole blood according to Bass contains between 6 

 and 10 mg. of purin nitrogen in 100 c.c. of blood. 



Schiller and Wiener (6) using Schitteiihelm's method found the free 

 purin bodies in the blood varied from 1.1 to 2.8 mg. in 100 c.c. of blood. 

 The uric acid formed between 25 and 50 per cent of the free purin bodies 

 in the blood. 



Thannhauser and Czoniczer give the nucleotid nitrogen of the blood 

 as varying in health between 2 and 3 mg. in 100 grams of serum. It was 

 about twice the amount of the free purin nitrogen. It is evident from these 

 studies that the combined purins are present in the blood in much larger 

 quantity than is free uric acid. 



Only slight variations have been observed in the amount of uric acid 

 in the blood of the same normal person at different times when on a purin 

 free diet. In four determinations made over a period of nearly two months 

 the uric acid varied only from 2.3 mg. to 2.5 mg. (McLester). Host (a) 

 maintains that on a purin free diet the uric acid in the blood is constant 

 for the normal individual. 



Denis(&) has shown that in health a period of high purin feeding last- 

 ing 5 to 10 days increases the uric acid in the blood only slightly (0.1 to 

 0.2 mg. per 100 grams) and sometimes it remains the same as on a purin 

 free diet. 



Uric Acid in the Organs and Tissues. The various tissues contain 

 quantities of free uric acid comparable to that in the blood of the same 

 person (Fine(a)). There is evidence that uric acid precursors are stored 

 in the liver (Rosenberg(a) (&)). Puncture of Claude Bernard's sugar 

 center in the brain produces in dogs a marked transitory incraase in the 

 output of allantoin, the end product of purin metabolism (Michaelis(a)). 

 This experiment suggests that uric acid like sugar is stored in the liver and 

 in a form that is readily available. 



Free uric acid introduced into the blood speedily disappears from the 

 circulation. This seemed probable from the observations of Bass(&) who 

 found that the blood two hours after an injection of uric acid contained 

 but little more uric acid (about 10 per cent of the uric acid injected) 

 than was present in the blood normally. The normal was determined 

 by an examination of the blood about ten days before or after the injec- 

 tion. The studies of McClure and Pratt clearly showed that uric acid 

 leaves the blood soon after its injection. The amount of uric acid was 

 determined at the time that 0.5 gram of uric acid with 1 gram of piperazin 



