THE ORGANIC CONSTITUENTS OF THE URINE. 247 



lactic acid, and ammonium carbonate, when given by the mouth, is 

 eliminated as such. Of the manner in which the synthesis of uric 

 acid is effected in the liver, however, we know but little. Urea or 

 ammonium carbonate cannot, of course, give rise to its formation 

 alone, as the available amount of carbon is too small. We must 

 hence assume that some other substance enters into the reaction. 

 This substance is as yet unknown, but we may imagine that ammo- 

 nium lactate may be formed as an intermediary product and that one 

 portion is first transformed into ammonium carbonate and that the uric 

 acid is then formed through the union of this with another molecule 

 of lactic acid. Horbaczewski, indeed, has shown that artificially 

 uric acid may be formed from lactic acid, ammonia, and carbon 

 dioxide, by heating trichloro-lactic amide together with urea. The 

 reaction which takes place may be represented by the equation : 



2CO(NH 2 ) 2 + C 3 C1 3 2 H 2 .NH 2 == NH 4 C1 -f 2HC1 -f H 2 O + C 5 H 4 N 4 O 3 . 

 Trichloro-lactic Uric acid, 



amide. 



On the other hand, it is possible that uric acid may result through 

 the union of glycocoll and urea, and artificially this synthesis can 

 indeed be effected. We have seen, moreover, that on hydrolytic 

 decomposition uric acid yields ammonia, carbon dioxide, and gly- 

 cocoll. In this case the resulting reaction could be expressed by 

 the equation : 



3CO(NH 2 ) 2 + CH 2 (NH 2 ).COOH = 3NH 3 + 2H 2 O + C 5 H 4 N 4 O 3 . 



Wiener has suggested that uric acid may be formed synthetically 

 through the union of tartronic acid with two urea radicles, and the 

 intermediate formation of dialuric acid, the tartronic acid being 

 itself derived from lactic acid by oxidation. This transformation is 

 represented by the following equations : 



NH 2 COOH NH CO 



II II 



1. CO + CHOH = CO CHOH + 2H 2 O 



N 



H 2 COOH NH CO 



Urea. Tartronic Dialuric acid, 

 acid. 



NH CO NH CO 



I I H 2 N\ I | 



2. CO CHOH + >CO = CO C H^ 



4, 



II H 2 N X >CO -f 2H 2 



m CO NH C HN X 



Dialuric acid. Urea. Uric acid. 



Wiener's experimental basis of the synthetic formation of uric 

 acid in birds is quite convincing and accords well with other 

 observed facts. 



While the greater portion of the uric acid is thus formed syn- 

 thetically in the liver of birds and reptiles, a variable but much 

 smaller amount results directly from the xanthin bases through 

 oxidation. 



