INTERMEDIATE METABOLISM OF THE FATS 411 



It is at the next succeeding stage of this process that trouble origi- 

 nates in the diabetic. In normal tissues the intermediate hydroxy- 

 and keto-acids are present only evanescently, being immediately oxi- 

 dized to the lower acid, carbon dioxide, and water. In the diabetic or 

 in the depancreatized animal there is exceptional difficulty in accom- 

 plishing this, it would appear, especially when the stage of butyric 

 acid has been reached and the result is that the partial products of 

 butyric acid oxidation, /3-hydroxybutyric acid and aceto-acetic acid 

 are permitted to accumulate : 



CH 3 CH 3 CH 3 



I I I 



/3CH 2 + O CHOH + O = CO + H 2 O 



I I I 



CH 2 CH 2 CH 2 



I I I 



COOH COOH COOH 



Butyric acid. |3-hydroxybutyric acid. Aceto-acetic acid. 



If, however, the number of carbon atoms in the original fatty-acid 

 molecule had chanced to be uneven instead of even, the final product 

 of this process would have been Propionic Acid, CH 3 CH 2 COOH instead 

 of butyric acid. 



Now the important discovery has been made by Ringer, that pro- 

 pionic acid is completely converted into Glucose in animal tissues, an 

 ^intermediate stage in the process being, not improbably, the formation 

 of 0-Lactic Acid: 



2CH 3 CH 2 COOH + O 2 = 2CH 2 OH.CH 2 COOH 

 Propionic acid. j8-lactic acid. 



He furthermore finds that when fatty acids having an uneven 

 number of carbon atoms are administered they are similarly trans- 

 formed, in part, into glucose. It happens, however, that the acid 

 radicals of the normal tissue-fats of our dietary always contain even 

 numbers of carbon atoms. The fatty acids possessing uneven numbers 

 of carbon atoms are comparatively rare, and do not occur to any 

 important extent in the fats of the normal dietary, otherwise their 

 administration to diabetics would enable them to transform the 

 residual unoxidized fragment of the fatty molecule into glucose, which 

 is harmless, instead of hydroxybutyric acid which is toxic. 



The normal products of the complete oxidation of butyric acid 

 according to the above scheme, would be, successively, Acetic Acid, 

 carbon dioxide and water: 



CH 3 CH 3 CH 3 CH 3 



I I I I 



/3CH 2 + O = CHOH + O = CO + 4O = COOH 



I I I 



CH 2 CH 2 CH 2 2CO 2 



I I I - 4- 



COOH COOH COOH H 2 O 



+H 2 O 



Butyric acid. /3-hydroxybutyric acid. Aceto-acetic acid, Acetic acid, carbon 



water. dioxide, water. 



