ALBUMINS OR PROTEINS. 237 



system, as does urea in the case of mammals. The analogy between uric 

 acid and urea has received further support from the discovery that the 

 same materials which produce an increase in urea in mammals, will cause 

 an increased elimination of uric acid in birds. Thus, von Knieriem l showed 

 such an influence by the administration of amino acids, while von Schroder 2 

 observed the same thing by feeding ammonium salts. Urea, 3 also, will 

 cause an increased elimination of uric acid. 



Minkowski 4 obtained a further insight into the production of uric acid 

 in birds, by extirpating the liver of geese. These animals will survive 

 the operation for 20 hours, because, in them, the portal vein is not the 

 only outlet of the splanchnic vessels, but is supplemented by another, 

 the Vena communicans. The elimination of nitrogen during this opera- 

 tion was somewhat diminished. The greatest change occurred in the 

 uric acid of the urine. Normal geese eliminate from 60-70 per cent of 

 the total nitrogen in the urine as uric acid, while those whose livers had 

 been removed showed only 3.6 per cent. Ammonia, in large amounts, 

 took the place of uric acid. Minkowski also noticed at the same time a 

 large amount of sarcolactic acid in the urine, a substance which is en- 

 tirely absent in the urine of normal geese. The question now arises, What 

 relation do the eliminated ammonia and lactic acid bear to the formation 

 of uric acid? 



We can imagine that the increased formation of ammonia arises from 

 a secondary process due to the appearance of the lactic acid. We are 

 aware of the fact that in ammonia the animal organism has a valuable 

 weapon to protect itself against acids. An increased appearance of 

 ammonia in the urine is very often a direct indication of an increased 

 production of acid in the organism. That the presence of the lactic acid 

 was an important factor in the increased production of ammonia is evident 

 from the fact that an addition of alkali caused an appreciable diminution 

 of the amount of ammonia in the urine. 5 At any rate, a part of the am- 

 monia must be looked upon as exerting a neutralizing effect. 



Hoppe-Seyler 6 has shown that the presence of the lactic acid was due 

 to a diminished oxidation in the tissues, as a result of the operation. It 

 is well known that a lactic acid formation often accompanies a dimin- 

 ished supply of oxygen. Minkowski 7 has replied to this objection by 

 showing that the total extirpation of the liver is not the only way an 



Z. Biol. 13, 36 (1877). 



Z. physiol. Chem. 2, 228 (1878). 



H. Meyer: Inaug. Diss. Konigsberg, 1877. 



Arch., exp. Path. Pharm. 21, 89 (1886); 31, 214 (1893). 



S. Lang: Z. physiol. Chem. 32, 320 (1901). 



Festschrift zu Vichow's 70 Geburtstag, 1891. Cf. also Araki: loc. cit. 



Arch. exp. Path. Pharm. 31, 214 (1893). 



