650 URINE. 



also been able to detect small quantities of carbamates in blood, and 

 later in conjunction with ABEL he detected carbamic acid in alkaline 

 horse's urine. DRECHSEL therefore accepts the theory of the formation 

 of urea from ammonium carbamate, and believes that the alternating 

 oxidation and reduction take place in the following way: 



H 4 N.O.CO.NH 2 + = H 2 N.O.CO.NH 2 + H 2 O 



Ammonium carbamate 



H 2 N.O.CO.NH 2 + H 2 = H 2 N.CO.NH 2 + H 2 0. 



Urea 



ABEL and MUIRHEAD 1 have later observed an abundant elimination 

 of carbamic acid in human and dog's urine after the administration of 

 large quantities of milk of lime, and the probability of the regular appear- 

 ance of this acid in normal acid-reacting human and dog's urine has been 

 demonstrated by M. NENCKI and HAHN 2 . These last-mentioned inves- 

 tigators have also given very important support to the theory of the 

 formation of urea from ammonium carbamate by observations on dogs 

 with ECK'S fistula. NENCKI and HAHN observed violent symptoms 

 of poisoning, in dogs fed on meat and operated upon by PAWLOW and 

 MASSEN, and these symptoms were quite identical with those obtained 

 on introducing carbamate into the blood. These symptom's also appear 

 after the introduction of carbamate into the stomach, while the intro- 

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

 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-transformation 

 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. 



The experience of ROTHBERGER and WINTERBERG was that the 

 phenomena with meat feeding and with carbamic acid intoxication are 

 not the same, and HAWK S has also arrived at other results. He 

 observed violent toxic symptoms on abandoning meat feeding with such 

 fistular dogs, but not always. In the latter cases the symptoms 

 appeared on the simultaneous feeding of LIEBIG'S extract of beef, while 

 this was without effect with a meat-free diet. The administration of 

 sodium carbamate or intravenous injection of this salt in dogs with 



1 Drechsel, Ber. d. sachs. Gesellsch. d. Wissensch., 1875. See also Journ. f. prakt. 

 Chem. (N. F.), 12, 16, and 22; Abel, Arch. f. (Anat. u.) PhysioL, 1891; Abel and 

 Muirhead, Arch. f. exp. Path. u. Pharm., 31. 



2 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. Pe"tersbourg, 1, No. 4, 1892. 



3 Rothberger and Winterberg, Zeitschr. f. exp. Path. u. Therap., 1; Hawk, Amer. 

 Journ. of PhysioL, 21. 



