ALBUMINS OR PROTEINS. 229 



the literature at hand, to draw a correct conclusion regarding the subject. 

 In very many cases we have contented ourselves with a more or less 

 exact method of determining the urea or its antecedents. This proof is 

 generally an indirect one. We shall, therefore, confine ourselves to the 

 most important investigations, abstracting only the essentials from each 

 of them. 



M. Nencki * characterizes the urea formation as analogous to a type of 

 synthesis, which takes place to a considerable extent in the animal organ- 

 ism; namely, the combination of two substances with elimination of water. 

 He uses the formation of hippuric acid from glycocoll and benzoic acid, as 

 an example: 



C 6 H 5 . CO .jOH + HjNH . CH 2 . COOH=C 6 H 5 CO . NH .CH 2 . COOH + H 2 0. 



Benzoie acid Glycocoll Hippuric acid 



Again, 



C 23 H39O3 . COOH + H . NH . CH 2 . COOH 



Cholic acid Glycocoll 



= C 23 H39O3 CO . NH . CH 2 .COOH + H 2 0. 

 Glycocholic acid. 



We can add other innumerable examples to these. We need only refer 

 to the formation of glycogen, fats, and albumin from their components, 

 and to the numerous examples of the conjugation of glycocoll, glucuronic 

 acid, and sulphuric acid, with other foreign bodies. Thus, we have as an 

 example of each : 



C 6 H 5 OH + HO . S0 3 K - C 6 H 5 . . S0 3 K + H 2 0. 

 Phenol Pot. phenolsulphate 



CioH 7 COOH + NH 2 . CH 2 . COOH=Ci H 7 CO . NH . CH 2 . COOH + H 2 O 



V - r - / V - v - / V - - -^- -- . - / 



Naphthoic acid Glycocoll Naphthuric acid 



3 .COH + C 6 H 10 7 = (CH 3 ) 3 . CO . C 6 H 9 6 + H 2 0. 



Trimethyl- Glucuronic Conjugated Glucuronic acid 

 carbinol acid 



M. Nencki considers the formation of urea from ammonium carbamate 

 to take place similarly by the elimination of water: 



NH 2 . CO . O . NH 4 = NH 2 . CO . NH 2 + H 2 0. 



Ammonium- Urea 



bamate 



Ber. 6, 890 (1872). 



