MECHANISM OF VITAL OXIDATION 99 



R.NH 3 NH 2 \ R.NH.CO.NH, 



I + CO = NH 3 + I 



COOH NH,/ COOH. 



It is sufficient, for example, to heat an alkaline urine contain- 

 ing tyrosin to steaming to effect such a transformation. 2 

 One must believe therefore that we are no longer justified 

 in any conclusions bearing upon the mechanism of urea 

 formation from the formation of these conjugate products. 

 From experiments in Hofmeister's laboratory 3 it was 

 determined that by perfusing the isolated living liver with 

 taurin the linking of CONH 2 , as above suggested, does not 

 directly take place; this group becoming available only if 

 glycocoll is introduced at the same time. The CONH 2 group 

 at all events appears from oxidation of the latter; whether, 

 however, from finished urea (as in the formation of a 

 uraminoacid from aminoacid and urea in the laboratory) or 

 from some precursor of urea, 



CHj.NH, CO.NH, . - CO.NHj 



COOH COOH CO, , 



cannot at present be determined. 



Mechanism of Vital Oxidation of Nitrogenous Sub- 

 stances. Schaniedeberg's anhydride theory is based on the 

 assumption that protein is burned in the living body to its 

 end-products, all the carbon eventually becoming C0 2 , all 

 the hydrogen water, the nitrogen appearing as ammonia, 

 just as in preparation of a protein for Kjehldahl determi- 

 nation.- 



At present the great riddle of the vital combustion proc- 

 esses, it is safe to say, is incomprehensible to us ; and it is 

 beyond our understanding how the living body manages at a 

 temperature less than 40 C. to effect an oxidation which in 

 the laboratory we are able to accomplish only by great heat 



2 H. D. Dakin, Jour, of Biol. Chem., 8, 25, 1910. 



8 P. Philosophow (F. Hofmeister's Lab., Strassburg), Biochem. Zeitschr., 

 26, 131, 1910; cf. therein Literature upon the Uraminoacids. 



