650 METABOLISM 



The most recent work of S. R. Benedict has shown that uric acid ex- 

 ists, chiefly in combination in the blood of most mammals but not in 

 that of the bird. It was found, for example, that fresh ox-blood exam- 

 ined by the Folin method contains only 0.0005 gm. free uric acid per 100 

 gm. of blood; after boiling the protein-free blood filtrate with hydro- 

 chloric acid, however, the uric acid increased by about ten times. This 

 larger amount was also found present in whole blood that had been 

 allowed to stand for some time, indicating that the uric-acid compound 

 can be split by means of an enzyme. The compound exists in the cor- 

 puscles and not in the plasma. It is of some significance that after thus 

 setting free the uric acid, there should be abflut 50 per cent more of it 

 present in the blood of the ox than in that of the bird, where most exists 

 in a free state in the serum, although the urine of the ox contains only 

 the smallest trace of uric acid, and that of the bird is loaded with it. 

 Investigation of the condition of uric acid in human blood is at present 

 in progress. 



Uriceinia in Gout and Nephritis 



The practical application of these observations is particularly impor- 

 tant in connection with the etiology of gout. In typical cases of this dis- 

 ease, the uric acid of the blood increases from its normal value of 1 to 

 3 mg. per cjent to nearly 10 mg., indicating a considerable degree of 

 renal insufficiency. This uricemia can not in itself, however, be the cause 

 of the deposition of urates in the joints, because it also occurs in other 

 diseases with renal retention, such as nephritis. Moreover, the blood 

 serum is capable of dissolving much larger quantities of uric acid than 

 are ever found present in it in gout. The real cause for the gouty deposits 

 must depend on some change affecting the blood so as to alter the form 

 in which uric acid exists therein, with the result that it is excreted into 

 the joints and deposited there. 



Other diseases showing uricemia are lead poisoning and nephritis. In 

 the latter disease the damaged excretory function of the kidney is 

 manifested first of all by an increase in the uric-acid content of the 

 blood, accompanied later by a retention of urea and later still by one 

 of creatinine. The severity of the renal involvement may therefore be 

 gauged by determining the percentage of these three metabolites. On 

 account of the importance of these facts from a clinical standpoint, we 

 append a table containing results secured by Myers and Fine, in which 

 the behavior of the metabolites in the blood is shown in relationship 

 to the severity of the case as gauged by the blood pressure. 



