THE AMIDO-ACIDS. 87 



the urea may result from uric acid by simple oxidation is possible, 

 and indeed probable, but the greater portion must of necessity 

 originate in a different manner. 



In birds, on the other hand, some of the uric acid apparently 

 results from glycocoll, and we thus see that in both classes of animals 

 the amido-acids may be the antecedents of the final products of 

 nitrogenous metabolism. 



It is conceivable that in mammals cyanic acid may be produced 

 as an intermediary product, and that urea then results through a 

 condensation of two molecules of this substance in datu nascendi, 

 according to the equation : 



/NH 2 



CQNH + CONH = CO< + CO 2 . 



X NH 2 



Then again we may imagine that a transformation of the amido- 

 acids occurs into the ammonium salts of the fatty acids standing 

 next in order in the downward scale, and that by further oxidation 

 these are transformed into ammonium carbonate, and this into urea. 

 It has been shown as a matter of fact that a fair amount of urea is 

 thus produced when blood containing ammonium carbonate or ammo- 

 nium formate is allowed to flow through the isolated livers of dogs. 

 According to Drechsel, finally, the amido-acids are transformed 

 into carbamic acid, from which urea may then result, as indicated by 

 the equation : 



/-i 



/NH 2 /NH 2 



C0< -f CO< = CO< + CO 2 + H 2 O. 

 X)H X)H \NH 2 



In a subsequent chapter this subject will be treated at greater detail. 



In addition to the important role which the amido-acids thus 

 play in the formation of urea, these bodies are of further interest 

 from the part which they take in some of the syntheses that 

 occur in the animal organism. In this manner they give rise to a 

 number of complex substances which can hence be regarded as 

 amido-derivatives. "With benzoic acid glycocoll thus combines to 

 form hippuric acid, as shown by the equation : 



CH 2 (NH 2 ).COOH_+ C 6 H 5 .COOH = CH 2 .NH(C 6 H 5 CO).COOH -f H 2 O 



Glycocoll. Benzoic acid. Hippuric acid. 



With phenyl-acetic acid glycocoll similarly combines to form 

 phenaceturic acid : 



CH 2 .(NH 2 ).COOH -f CH 2 .(C,H 5 ).COOH = 



C 6 H 5 .CH 2 .CO - NH.CH 2 .COOH + H 2 O. 



That uric acid on hydrolytic decomposition will yield ammonia, 

 carbon dioxide, and glycocoll has been shown. There is evidence, 

 moreover, to show that in the organism of birds and reptiles, at 

 least, its synthesis can similarly occur. 



Ornithuric acid results through the union of benzoic acid with the 

 diamide ornithin : 



