510 URIC -ACID METABOLISM AND GOUT 



the large amount of purin bodies brought to the liver from the 

 animal food of the carnivora. In man the kidney is also most 

 active, although if the bulk of the organs be taken into account, 

 in man the muscles destroy most uric acid, next the kidneys, 

 and then the liver (Croftan). The destruction seems to be 

 accomplished by specific uricolytic enzymes, which are of the 

 nature of oxidizing enzymes, although it may be that some 

 other enzymes must first split the uric-acid molecule to prepare 

 it for oxidation. 



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 purin bodies taken in the food, upon which, chiefly, depends 

 the amount of exogenous uric acid. (2) The amount of destruc- 

 tion of tissue nucleoproteids. (3) The amount of purin bases 

 formed in the muscle tissue. (4) The amount of conversion 

 of purin bases into uric acid. (5) The amount of destruction 

 of uric acid occurring in the body. (6) Possibly upon the 

 capacity of the tissues to synthesize 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 quanti- 

 ties of uric acid when all the above-mentioned factors, especially 

 the diet, are not controlled and taken into consideration. Yet 

 on just such an inadequate basis has been constructed an 

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

 " uric-acid intoxication/' " lithemia," etc., until it has come 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 be 

 safely stated that at the present time there exists no good 

 evidence which makes it probable that uric acid is responsible 



