634 URIC-ACID METABOLISM AND GOUT 



evidence, however, that any of these alternative routes is ever fol- 

 lowed in the animal body. It 'is possible that the failure to find all 

 the purines of the food as uric acid in the urine depends on their par- 

 tial destruction in the intestine by bacteria.-* It is highly probable, 

 in view of all available evidence, that in man most of the purine ab- 

 sorbed from the food, and practically all the purine from cell metabo- 

 lism, is converted into uric acid and excreted as such. 



THE OCCURRENCE OF URIC ACID IN THE BLOOD, TISSUES, AND URINE 



As can be seen from the foregoing discussion, the amount of uric 

 acid that appears in the urine depends upon a number of factors, 

 which may be enumerated as follows:-^ (1) The amount of purine 

 bodies taken in the food, upon which, chiefly, depends the amount of 

 exogenous uric acid. (2) The amount of destruction of tissue nucleo- 

 proteins. (3) The amount of purine bases formed in the muscle tis- 

 sue. (4) The amount of conversion of purine bases into the uric 

 acid. (5) The amount of destruction of uric acid, if any, occurring 

 in the body. (6) Possibly upon the capacity of the tissues to synthe- 

 size uric acid; and in case such power to synthesize uric acid exists, 

 upon the presence of the precursors of uric acid in the body. (7) The 

 retention of uric acid in the blood and tissues. (8) The power of the 

 kidneys to excrete uric acid. 



If we also take into account the fact that the solubility of uric acid 

 in the urine depends chiefly upon the amount of neutral phosphates 

 present in the urine, and also upon the temperature, reaction, and 

 concentration of the urine, it becomes apparent how totally devoid of 

 significance is the presence of crystals of uric acid and urates in the 

 urine, and how fallacious is any theorization based upon the excretion 

 of considerable quantities of uric acid when all the above-mentioned 

 factors, especially the diet, are not controlled and taken into consid- 

 eration. Yet on just such an inadequate basis was once constructed 

 an enormous amount of theorization as to ''uric-acid diathesis," 

 "uric-acid intoxication, " "lithemia, " etc., until it came to be popularly 

 believed that a large share of the minor ailments of humanity, and in 

 particular all non-infectious diseases of the joints and muscles, are 

 dependent upon the presence of excessive quantities of uric acid or 

 urates in the blood. But it may safely be stated that at the present 

 time there exists no good evidence which makes it probable that uric 

 acid is responsible for any pathological conditions whatever, except 

 uric-acid calculi, "uric-acid infarcts" in the kidneys, and certain 

 manifestations of gout. Uric acid is possessed of but a very shght 

 degree of toxicity, and the body is able to get rid of it in such large 



" See Siven, Arch. ges. Physiol., 1914 (157), 582; Thannhauser and Dorf- 

 muUor, Zeit. physiol. Chem., 1918 (102), 148. 



2"^ Review on uric acid metabolism and many data given by Host, Nord. Mag. 

 Laev., 1917 (78 Suppl.). See also Jour. Biol. Chem., 1919 (38), 17. 



