FORMATION OF UREA. 651 



EcK-fistula did not, on the contrary, produce the same toxic symptoms 

 as occurred where meat and extract were fed, and these observations 

 on these fistular animals do not allow of any positive conclusions as 

 to the relation of the carbamates to the formation of urea. On the 

 other hand neither do they contradict the assumption of such a mode 

 of formation of the urea. 



Besides the above view of the formation of urea from ammonium 

 carbonate and carbamate, which has been called the anhydride theory, 

 we also have the oxidation theory of HOFMEISTER. 



F. HOFMEISTER 1 found in the oxidation of different members 

 of the fatty series, as well as in amino-acids and proteins, that urea was 

 formed in the presence of ammonia, and he therefore suggests the pos- 

 sibility that urea may be formed by an oxidation-synthesis. Accord- 

 ing to him, in the oxidation of nitrogenous substances a radical CONH^ 

 containing the amide group, unites at the moment of formation with the 

 radical NH 2 remaining on the oxidation of ammonia, forming urea. 



Besides the above-mentioned theories as to the formation of urea, 

 there are others which will not be given, because the only theory which 

 has thus far been positively demonstrated is the formation of urea in 

 the liver from ammonium compounds and amino-acids. 



The liver is the only organ in which, up to the present time, a forma- 

 tion of urea has been directly detected; 2 and the question arises, what 

 importance has this urea formation which takes place in the liver? Is 

 the urea wholly or chiefly formed in the liver? 



If the liver is the only organ capable of forming urea, it is to be 

 expected, on the extirpation or atrophy of that organ, that a reduced 

 or, in short experiments, at least a strongly diminished elimination of 

 urea should occur. As at least a part of the urea is formed in the liver 

 from ammonium compounds, a simultaneous increase in the elimination 

 of ammonia is to be expected. 



The extirpation and atrophy experiments made on animals by dif- 

 ferent methods by NENCKI and HAHN, SLOSSE, LIEBLEIN, NENCKI 

 and PAWLOW, SALASKIN and ZALESKI S have shown that sometimes a 

 rather marked increase of ammonia and a diminished elimination of 

 urea takes place after the operation, but that there are also cases in 



1 Arch. f. exp. Path. u. Pharm., 37. 



2 In regard to the investigations of Prevost and Dumas, Meissner, Voit, Grehant, 

 Gscheidlen and Salkowski, and others, on the role of the kidneys in the formation of 

 urea, see v. Schroeder, Arch. f. exp. Path. u. Pharm., 15 and 19, and Voit, Zeitschr. 

 f. Biologic, 4. 



3 Xencki and Hahn, 1. c.; Slosse, Arch. f. (Anat. u.) Physiol., 1890; Lieblein, Arch, 

 f. exp. Path. u. Pharm., 33; Nencki and Pawlow, Arch, des scienc. biol. de St. P6ters- 

 bourg, 5. See also v. Meister, Maly's Jahresber., 25; Salaskin and Zaleski, Zeitschr. f . 

 physiol. Chem., 29. 



