684 URINE. 



and HAHN have made further observations on dogs with Eck's fistula, 

 which substantiate this view. In such fistula dogs, they observed that 

 when meat was fed, violent poisonous symptoms developed which were 

 almost identical with those produced when carbamate was introduced 

 into the blood. The same symptoms also appeared on the introduction 

 of carbamate into the stomach of the fistula animal, while the intro- 

 duction of carbamate into the stomach of a normal dog had no action. 1 

 As these observers also found that the urine of the dog on which the 

 operation was made was richer in carbamate than that of the normal 

 dog, they concluded that the symptoms were due to the non-transforma- 

 tion of the ammonium carbamate into urea in the liver, and they consider 

 the ammonium carbamate as the substance from which the urea is derived 

 in the mammalian liver. 



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 2 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 CONH2, 

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

 radical NH2 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; 3 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 



1 Hahn, Massen, Nencki et Pawlow, La fistule d'Eck de la veine cave inferieure et 

 de la veine porte, etc. Arch, des sciences biol. de St. Ptersbourg, 1, No. 4, 1892. 

 In regard to certain differences between the symptoms with carbamate poisoning and 

 after meat feeding with Eck fistula dogs, see Rothberger and Winterberg, Zeitschr. 

 f . exp. Path. u. Therap., 1; Hawk, Amer. Journ. of Physiol., 21. 



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



3 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. 



