FAT METABOLISM 713 



We may conclude from this that the double linkage in the oleic acid of the depot fat 

 exists between the ninth and tenth C-atoms. But it is otherwise in the case of the un- 

 saturated acid from the liver (pig's), for under the above process of oxidation this 

 yielded caproic acid, which, since this acid has six C-atoms, would indicate that the 

 double linkage existed between the sixth and seventh C-atoms. Another interesting fact 

 brought to light by the experiments was that a tetraoxystearic acid was formed, which 

 fell apart in such a way as to indicate that the hydroxyl groups occurred between the sixth 

 and seventh and between the ninth and tenth C-atoms. The occurrence of this substance 

 would be satisfactorily explained by the introduction into the molecule of oleic acid of a 

 second double bond i. e., between the sixth and seventh C-atoms. ' ' The acids found in 

 the pig's liver may be accounted for, in other words, by supposing that desaturation 

 of stearic acid and of the ordinary (depot) oleic acid occurs by the introduction of a 

 double link between the sixth and seventh carbon atoms in each case" (Leathes). Still 

 other double links may, however, be introduced into the fatty-acid chain, for acids of the 

 linolic acid series are present in cod-liver oil. Finally, it is of interest to note that caproic 

 acid is a product of the above oxidation process, for it has an even number of C-atoms 

 and therefore will form |3-oxybutyric acid. 



To go into these chemical problems any further here would be out of 

 place. One other fact, should, however, be borne in mind namely, that 

 the unsaturated acids may be formed from saturated acids through the 

 intermediate formation of /?-hydroxy and /?-ketonic acids. Their mere 

 presence, in other words, should not be taken as evidence that the oxida- 

 tion of fatty acids is initiated by the introduction of an hydroxyl group 

 at the (3 position in the chain. 



