METABOLISM, NUTRITION AND DIETETICS 441 



for six to twenty hours. While in the normal goose 50 

 to 60 per cent, of the total nitrogen is eliminated as uric 

 acid in the urine, and only 9 to 18 per cent, as ammonia, 

 in the operated goose uric acid represents only 3 to 6 per 

 cent, of the total nitrogen, and ammonia 50 to 60 per cent. 

 A quantity of lactic acid equivalent to the ammonia appears 

 in the urine of the operated animal, none at all in the urine 

 of the normal bird. The small amount of urea in the 

 normal urine of the goose is not affected by extirpation of 

 the liver. And while urea, when injected into the blood, 

 is in the normal goose excreted as uric acid, it is in the 

 animal that has lost its liver eliminated in the urine 

 unchanged. 



(4) After removal of the liver in frogs, or in dogs which 

 have survived the previous connection of the portal vein with 

 the inferior vena cava by an Eck's fistula (p. 328), the quantity 

 of urea excreted is markedly diminished, and the ammonium 

 salts in the urine are increased. When the Eck's fistula is 

 established and the portal vein tied, without any further 

 interference with the hepatic circulation, the amount of urea 

 in the urine is not lessened to nearly the same extent, 

 evidently because the substances from which urea is formed 

 still, for the most part, gain access to the liver through the 

 hepatic artery and by means of the back-flow which is known 

 to take place through the hepatic vein. If the animals are 

 kept on a diet poor in proteids, no symptoms may develop 

 for a considerable time. But if much proteid is given, char- 

 acteristic symptoms, including convulsions, always appear. 

 These seem to be produced by the saturation of the organism 

 with ammonia compounds, which are formed from the pro- 

 teids as in the normal animal, but which the liver, w r ith its 

 circulation crippled, is unable to cope with and to completely 

 change into urea. Although the portal vein carries to the 

 liver a much greater supply of blood than the hepatic artery, 

 ligation of the latter causes a greater diminution in the ratio 

 of the amount of urea to the total nitrogen in the urine than 

 ligation of the former. This seems to indicate that oxidation 

 plays an important part in the formation of urea in the liver 

 (Doyon and Dufourt). 



