THE OXIDATION PROCESS 



203 



Continuing up the series, phenyl-propionic acid is excreted 

 as hippuric acid, showing that two atoms of carbon have 

 first been spht oi! and benzoic acid formed. 



The next member of the series, phenyl-butyric acid, is 

 excreted as phenaceturic acid, showing that it has first 

 been oxidised to phenyl-acetic acid. And so on alternately. 

 These facts may be tabulated thus : — 



Benzoic . 

 Phenyl acetic . 

 Phenyl propionic 

 Phenyl butyric 

 Phenyl valeric 



Acid fed. 



CeH^COOH 

 CsHsCHjCOOH 

 OsHsCH/JHaCOOH 

 , C.HsCH^OHjOHaCGOH 

 CjHjOHjOHjOHeCHjCOOH 



Oxidised to 



(not oxidised) 

 (not oxidised) 



C'eUjCOOH 



OeH.OHjCOOH 



C'dHsCOGU 



Excreted as 



CeHsCONHOHjCOOH 

 OeHsCHjCONHOHjOO OU 

 CsHsCONHCHjCOOH 

 OeHsCHjCONHCHjGOOU 

 CeHjCONHCHjCOOH 



It will be seen that the number of carbon atoms spht 

 ofE is always even. Phenyl valeric acid would appear to 

 be oxidised thus : — 



CfiHrCHoCHoCHn 



CHoCOOH 



CeHsCHaCHaCOOH 

 CeH^COOH. 



As to the oxidation of the two-carbon-atom chain we 

 have no certain information. 



8.— THE OXIDATION PROCESS 



The nature of the oxidation of the foodstuffs is not yet 

 completely elucidated. How are substances such as fats, 

 which normally are so difficult of oxidation at body tem- 

 perature, oxidised so easily in the tissues ? Why, under 

 certain circumstances, can some foods be oxidised and not 

 others, as in diabetes 1 



It is beheved that the oxygen must first be converted 

 into atomic form through the formation of certain peroxides. 

 A large number of substances, including aldehydes, carbo- 

 hydrates, etc., undergo on exposure to oxygen at ordinary 

 temperature slow oxidation, with intermediate formation of 

 peroxides. An example is seen in the case of benzaldehyde — 



QH.CHO -f 0., - CeH.CO . . OH. 



Benzoyl hydrogen peroxide. 



