ALBUMINS OR PROTEINS. 231 



sponded exactly with the amount of nitrogen added in the form of sal- 

 ammoniac. The results were not so definite with human beings and. dogs. 

 A part of the ammonia appeared in the urine, and, from the uncertain, 

 increase of urea, it remained undecided whether this was due to the am- 

 monia diet or an increased disintegration of albumin. The cause of the 

 different behavior between the carnivora and the herbivora was soon dis- 

 covered. It depends on the following: The food of the herbivora yields 

 an alkaline ash, and during its combustion in the organism it forms potas- 

 sium carbonate which can react with ammonium chloride. Ammonia 

 is liberated, and can then be utilized for the production of urea. The 

 conditions are entirely different with the carnivora. Its food furnishes 

 an acid ash. The hydrochloric acid is not separated from the ammonia 

 in the tissues, and consequently the latter is not available for the produc- 

 tion of urea. If, on the other hand, we feed some ammonium carbonate 

 to a dog, we likewise observe an increase of urea. These experiments, 

 therefore, indicate that the organism of mammals is capable of utilizing 

 ammonia for the production of urea. 



The observations of N. Nencki, J. Pawlow, and J. Zaleski * have indicated 

 the probability that ammonia normally i.e. without being artificially 

 administered participates in the formation of urea. They showed that 

 portal blood contained much more ammonia than did the venous blood of 

 the liver. The intestine evidently sends ammonia to the liver, where it is 

 transformed. If the liver be extirpated, we no longer observe any dif- 

 ference between portal blood and that obtained from any other part of 

 the body. 



W. v. Schroder 2 has shown that the liver can produce urea from am- 

 monium carbonate and ammonium formate. He passed blood, to which 

 he had added these ammonium compounds, through the liver of a dog, and 

 could soon detect an increase in the amount of urea therein. There can, 

 therefore, no longer be any doubt that the liver plays a very important 

 part in the production of urea. Analogous experiments were carried out 

 with the kidneys and muscles, without, however, showing any increase in 

 the formation of urea in these organs. 



That the liver is not to be looked upon as the only place where urea is 

 formed, is evident from the fact that its production is continued, even if 

 less in amount, after the liver has been entirely extirpated. These dis- 

 coveries only became possible after it was known how to make the so- 

 called " Eck's fistula." 3 Mammals do not tolerate the complete extir- 

 pation of the liver. They die shortly after the operation. They can, 



1 Arch. exp. Path. Pharm. 37, 26 (1895). 

 3 Arch. exp. Path. Pharm. 15, 364 (1882) ; 19, 373 (1885). 



3 M. Hahn, O. Massen, M. Nencki, and J. Pawlow. Arch. exp. Path. Pharm. 32, 

 161 (1892). 



