648 URINE. 



interest since KOSSEL and DAKIN have discovered the presence of an 

 enzyme, arginase, in the liver and other organs, which has the power 

 .-of splitting arginine with the formation of urea. THOMPSON 1 has recently 

 given a direct proof for the formation of urea from arginine. The 

 introduction of arginine into the body of a dog either per os or sub- 

 cutaneously has in his experiments led to an elimination of urea. While 

 outside of the body only one-half of the nitrogen of arginine is split 

 off as urea and the other half as ornithine, in the above experiments 

 the increase in urea in several instances corresponded to the greater 

 part if not the whole of the nitrogen of the arginine introduced. In 

 these cases, without mentioning that the arginine seemed to raise the 

 nitrogen catabolism, probably also urea was formed from the ornithine. 

 This can be explained by a deamidation of the ornithine and formation 

 of urea from the ammonia and carbon dioxide split off. 



By the action of alkalies, as above mentioned (Chapter XI), urea 

 may be formed from creatinine; still such an orgin of urea in the animal 

 body has not thus far been proven. 



The amino-acids are considered as special mother-substances of urea. 

 By the researches of SCHULTZEN and NENCKI and SALKOWSKI with 

 leucine and glycocoll, those of STOLTE with several amino-acids, and 

 those of v. KNIERIEM with asparagin, it has been shown that the amino- 

 acids are in part converted into urea in the animal organism. The 

 investigations by SALASKIN with the three amino-acids, glycocoll, leucine, 

 and aspartic acid, have unmistakably shown that the surviving dog- 

 liver, supplied with arterial blood, has the property of transforming the 

 above amino-acids into urea or a closely allied substance. The researches 

 of LOEWI with the " urea-forming " enzyme of the liver, discovered by 

 RICHET, on glycocoll or leucine, as also the researches of AscoLLi, 2 

 have led to similar results, but it must be remarked that we have no 

 proof as to the identity of the newly formed substance with urea. The 

 formation of urea from amino-acids is considered as proven, and, like 

 the amino-acids, the polypeptides are also decomposed into urea in 

 the animal organism, as shown by ABDERHALDEN with TERUUCHI and 

 BABKIN and with ScniTTENHELM. 3 



Nothing positive can be said in regard to the manner in which this 



1 Kossel and Dakin, Zeitschr. f. physiol. Chem., 41; Thompson, Journ. of Physiol., 

 32 and 33. 



2 Schultzen and Nencki, Zeitschr. f. Biologic, 8; v. Knieriem, ibid., 10; Salkowski, 

 Zeitschr. f. physiol. Chem., 4; Salaskin, ibid., 25; Loewi, ibid., 25; Stolte, Hofmeister's 

 Beitrage, 5; Richet, Compt. rend., 118, and Compt. rend. Soc. biol., 49; Ascoli, 

 Pfliiger's Arch., 72. 



3 Abderhalden with Teruuchi and with Babkin, Zeitschr. f. physiol. Chem., 47, 

 with Schittenhelm, ibid., 51. 



