THE ORGANIC CONSTITUENTS OF THE URINE. 237 



forced to the conclusion that the greater portion of the urea must 

 originate in a different way. 



It has been repeatedly shown that during the decomposition of 

 the albumins by means of acids and alkalies, as also during the 

 process of tryptic digestion and albuminous putrefaction, mono- 

 amino-acids result in large quantity. It has hence been supposed 

 that these bodies may also represent intermediary products in the 

 transformation of the tissue nitrogen into urea, which latter has 

 generally been regarded as the end-product of the nitrogenous 

 metabolism of the tissues. It has been shown as a matter of fact 

 that in mammals and to these I shall confine my remarks for the 

 present the administration of such acids in the food is followed by 

 a corresponding increase in the amount of urea. Under certain 

 pathological conditions, moreover, they appear in the urine as such, 

 and it is then noted that the elimination of urea is much diminished. 

 In health, however, this does not occur, and on examination of the 

 different tissues and organs of the body ami no-acids are found only 

 in traces. We must hence assume, supposing them to occur as 

 primary products of albuminous decomposition within the body, 

 that they are transformed at once into other substances, which in 

 turn give rise to urea. As all the amino-acids on oxidation yield 

 ammonium carbonate, this substance would suggest itself as a 

 possible antecedent of urea. We find, as a matter of fact, that 

 ammonium carbonate when ingested by the mouth, or otherwise 

 introduced into the body, appears in the urine as urea. This trans- 

 formation of mono-amino-acids into urea may be represented by the 

 following equations : 



(1) CH 2 (NH 2 ).COOH + 2O = H.COONH 4 -f CO 2 



Glycocoll. Ammoimim 



formate. 



(2) 2H.COONH 4 + 2O = (NH 4 ) 2 .CO 3 + H 2 O -f CO a 



(3) (NH 4 ) 2 .C0 3 = C0<^ -f 2H 2 



Urea. 



Drechsel has further shown that the amido-acids yield carbamic 

 acid on oxidation, and that through alternate oxidation and reduction 

 urea can result from the ammonium salt, as shown in the equation : 



/NH 2 NH 2 



OC< = OC( + H 2 



X).NH 4 X NH 2 



That carbamic acid is present in the normal acid urine of man 

 and the dog has been proved. Nencki and Hahn, moreover, 

 observed that in dogs in which the liver was temporarily excluded 

 from the general circulation larger amounts of carbamic acid 

 appeared in the urine than under normal conditions, and that the 

 animals showed symptoms of intoxication identical with those 

 observed when carbamates are directly introduced into the blood- 



