CHEMISTRY OF THE LIVER. 315 



the most thoroughly studied. The older notion of the forma- 

 tion of urea from the more complex uric acid is no longer 

 held; indeed no simple relation exists between the two sub- 

 stances, as it is pretty well established that the destruction of 

 the nuclein bodies is mainly responsible for the uric acid of 

 the urine. A great many observations unite in suggesting the 

 liver as the organ in which urea is most abundantly produced, 

 and certain ammonium salts as being largely or mainly con- 

 cerned in this production. 



It has been noted clinically that in diseases of the liver there 

 may be at the same time a marked diminution in the excretion 

 of urea with a corresponding increase in the ammonia excre- 

 tion. It is also known that the administration of ammonium 

 salts is not followed by an increase of ammonia in the urine. 

 Parallel with this observation we have the further one made 

 on the blood, which has shown that the fluid of the portal vein 

 is far richer in ammonia than is that from the hepatic vein. 

 Such observations have been followed up by experiments in 

 which fresh blood is forced through a living or a recently 

 removed liver by means of specially constructed apparatus. 

 The same blood may be caused to pass the liver many times. 

 After passing a few times and reaching uniformity in compo- 

 sition various ammonium and related compounds are added 

 to the blood and the circulation then continued. In this way 

 the abundant transformation of ammonium carbonate into 

 urea is readily shown. It has also been found that certain 

 amino acids are converted rather readily in going through the 

 liver. Experiments have shown that in the course of a few 

 hours several grams of leucine, glycocoll or aspartic acid may 

 be transformed into urea under these unfavorable conditions. 



The importance of this observation will be recognized. It 

 is well known that the amino acids are among the most im- 

 portant of the disintegration products of the proteins; by 

 hydrolytic and other cleavage reactions these amino complexes 

 result, and we see here the possibility of further destruction 

 with ultimate formation of urea. It is possible that in this 



