io8 



BIOLOGICAL CHEMISTRY 



carbon atoms at a time. The following table* illustrates this 

 point, the excretory products being the compounds formed 

 by uniting the aromatic acids with glycine NH 2 CH 2 COOH : 



TABLE XVIII 



These results indicate that the oxidation always occurs at 

 the second carbon atom from the carboxyl group, or in 

 chemical nomenclature in the p position, f Further support 

 to the jff-oxidation hypothesis is given by the formation of 

 /3-hydroxybutyric and of aceto-acetic acid in diabetes and 

 other conditions, especially when large quantities of fat are 

 being oxidised. 



It is believed that /Miydroxybutyric acid and aceto-acetic 

 acid are normal stages in metabolism, but that they are 

 relatively less easily oxidised than the other stages. Hence 

 when large quantities of fat are being used they accumulate 

 in the cells, escape into the blood and appear in the excretions. 



Their presence in large quantities is dangerous because 

 they must be neutralised by the alkalies of the body ; there- 

 fore, the body suffers from loss of alkali and coma results. 

 Perfusion of various acids through the liver gives rise to 

 aceto-acetic acid (CH 3 COCH 3 COOH), as shown by the 

 following table.J 



TABLE XIX 



Normal Fatty Acid. Formation of aceto- 



acetic acid. 



Acetic Acid, CH 3 COOH 



Propionic Acid, CH 3 CH 2 COOH 



Butyric Acid, CH 3 CH 2 CH 2 COOH + 



Valeric Acid, CH 3 CH 2 CH 2 CH 2 COOH 



Caproic Acid, CH 3 CH 2 CH 2 CH 2 CH 2 COOH + 



Heptylic Acid, CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 COOH 



Octoic Acid, CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 COOH + 



Nonoic Acid, CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 COOH 



Decoic Acid, CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 COOH + 



* H. D. Dakin, loc. cit., p. 18. 



f F. Knoop, Beit. z. chem. Physiol. u. Path., 1904, vol. 6, p. 150. 



J From H. D. Dakin, loo. cit., p. 21. 



