URIC ACID. $9$ 



Variations in the amount. (a) The relation to urea; the effects 

 of diet. Variations in the quantity of uric acid have been considered 

 from two different points of view. By some, these variations have 

 been expressed always in relation to the quantity of urea excreted 

 simultaneously. Such observers have felt that an increase or decrease 

 in uric acid, which merely accompanies a corresponding change in the 

 general nitrogenous metabolism, is of less physiological significance than 

 a variation which occurs independently of (or out of proportion to) the 

 latter ; and since the urea excretion is a measure of this general 

 metabolism, the uric has been, by such writers, referred to the urea 

 output as a standard. Other and more recent authorities, seeing the 

 origin of uric acid in an entirely distinct series of events within the 

 body, and observing that the urea : uric acid ratio has no stable 

 value, have recommended the entire neglect of this relation, prefer- 

 ring to express the uric acid output always in terms of its absolute 

 amount. 



An attempt has been made to show that urea and uric acid are 

 always produced in the body, so as to bear a constant and definite ratio 

 to each other, and that any alterations in this ratio indicate either a 

 retention of uric acid on the one hand, or a sweeping out of previously 

 retained acid on the other. 1 That this position cannot be maintained in 

 its entirety is quite certain. Consideration of the effect of varying diet 

 alone gives sufficient evidence against it. If the two analyses by Bunge, 

 given in an early section of this article, be examined, we see that upon a 

 diet of bread, not only is the absolute amount of uric acid less than upon 

 a diet of beef, but also that the relation to urea is also strikingly less. 

 On bread the ratio is 1 to 81, on beef it is 1 to 48. Similar results are 

 obtained, as the writer has found, if the experiments are continued for 

 many days. If the two substances were always produced in constant ratio 

 we should have to conclude that a bread diet produces a continuous 

 storing up of uric acid in the body ; and for this conclusion there is 

 certainly no evidence. 



Again, if we consider the effect of varying the quantity of the 

 ingested food its composition being maintained uniform we find that 

 on the whole the uric-acid excretion is less affected by such variations 

 than is the urea, so that we change the value of the ratio merely by 

 altering the amount of food taken. 



It is therefore impossible to look upon the ratio which uric acid 

 bears to urea as an independent physiological constant, or to conclude 

 that even wide variations in its value are necessarily pathological. 



But some authorities go further than to say that the uric acid 

 output is more stable than that of the urea, claiming, indeed, that it is 

 quite unaffected by the absorption of the ordinary proteids of diet the 

 albumins and globulins with their derivatives. If this be a fact, and 

 the production of the acid is independent of variations in these main 

 nitrogenous constituents of food, we ought certainly, in studying the 

 quantity in the urine, to neglect its ratio to urea altogether. This ratio 

 will then be little more, under ordinary circumstances, than an expression 

 for the urea variations, measured from the more stable uric acid output, 

 so to speak, as a base line ; while, if we are studying the effect of special 

 factors upon uric acid production, reference to the urea will be un- 

 necessary and misleading. 



1 Haig, "Uric Acid in Disease." 

 VOL. I. 38 



