238 LECTURE XI. 



excretion of lactic acid can be caused, but that even ligating the vessels 

 of the liver is sufficient to bring this about. Lactic acid will only appear 

 in the urine at the moment when the last branch of the hepatic artery has 

 been tied. There is no lactic acid formed, if a single branch is left free. 



Kowalewski and Salaskin 1 have shown that the appearance of lactic 

 acid after the extirpation of the liver is actually to be traced back to a 

 disturbance in the formation of uric acid. They could detect the forma- 

 tion of lactic acid by merely leading ammonium-lactate through the liver 

 of birds. H. Wiener 2 also showed relations between the lactic acid and 

 the formation of uric acid. He fed lactic acid and urea to birds, and 

 noticed an increase in the uric acid. 



In order to give an idea of the relationship of lactic acid to uric acid 

 it will be necessary to give the constitution of uric acid. It is a 2, 6, 8 

 trioxypurine: HN C=O 



O-U 



-NH 



I I >CO 



:N c ] 



HN C NH 



Uric acid 



Horbaczewski has obtained it synthetically by heating urea and glycocoll 

 together, and also by heating trichlorlactamide with an excess of urea. 

 Uric acid is decomposed on strongly heating into urea, hydrocyanic acid, 

 cyanuric acid, and ammonia. If uric acid is heated with concentrated 

 sulphuric acid in a sealed tube at 170 C. it breaks up into glycocoll, carbon 

 dioxide, and ammonia. Strecker, 3 to whom we owe this discovery, com- 

 pares the uric acid production from the components glycocoll and cyanic 

 acid with the production of hippuric acid from glycocoll and benzoic acid. 



We observe from this that the synthesis of uric acid from lactic acid 

 and ammonia, or urea, is a very plausible one. The standpoint that 

 uric acid is a direct degradation product of albumin has long been dis- 

 carded. Uric acid, which obtains its nitrogen from albumin, can only be 

 produced synthetically. We wish to call attention at this point to the 

 very close analogy between the production of uric acid and that of urea. 

 It can be shown in both cases that ammonia, directly or indirectly, plays 

 a part, as does also an acid (carbonic acid or lactic acid) . The ammonia 

 in both cases may have the same origin, being derived from albumin or its 

 cleavage-products. The organisms of the birds and reptiles evidently are 

 also capable of causing the removal of the NH 2 group. This is appar- 



1 Z. physiol. Chem. 33, 210 (1901). 



2 Verb. XVII, Kong. Med. 1889, p. 622, and Arch. exp. Path. Pharm. 42, 375 

 (1899); Verb. XIX, Kong. Med. 1901, 383. Hofmeister's Beit. 2, 42 (1902). Cf. also 

 H. Wiener: Die Hamsaure, Ergebnisse der Physiologic (Asher and Spiro) 1, I, 555 

 (1902). 



3 Ann. 146, 142 (1868). 



