124 III. OXIDATION AND METABOLISM 



foodstuffs metabolized. Total glucose and total fatty acids were calculated 

 as follows: 



Glucose = C + 0.58 P + 0.1 F 

 Total fatty acids = 0.46 P + 0.9 F 



C = carbohydrate 



F = fat 



P = protein 



The glucose arising from protein is calculated on the basis of the accepted 

 hypothesis that protein gives rise to 58% glucose. In the case of fat, the 

 glycerol which is converted to glucose is 10% of the total weight of this 

 foodstuff metabolized. Protein is believed to give rise to 46% fatty acids, 

 while 90% of the fat molecule is known to be made up of fatty acids. 

 Woodyatt stated that one g. of carbohydrate must be available to effect the 

 complete oxidation of 1.5 g. of fatty acid, giving a fatty acid: glucose ratio 

 (F.A. :G) of 1.5: 1 as the threshold of ketosis. Since the molecular weight 

 of glucose is 180 and the average value for the molecular weight of palmitic 

 and oleic acids is 270, this would entail a F.A./G. ratio on the molecular 

 basis of 1 : 1, which is only one-half that cited by Shaffer. -^^ 



Although these calculations were widely employed for the determination 

 of satisfactory diets to prevent ketosis, and there has been considerable 

 discussion as to which formula and method of calculation is correct, less 

 emphasis has been placed on this subject since the advent of the insulin 

 treatment of diabetes. Moreover, it should be pointed out that, on a 

 theoretical basis, the calculations are not correct, in line with our present 

 knowledge. In the first place, it is now known that several ketone molecules 

 are formed for each long-chain fatty acid molecule.^^-^^-^^"^*-^^'''^'*'* Sec- 

 ondly, no account is taken of the well-known fact that a difference in sus- 

 ceptibility to ketonuria exists between men and women. ^^^ 



b. Sources of Ketone Bodies in the Animal, (a) Formation from Even- 

 Chain Fatty Acids. The principal sources of the ketone bodies in the 

 animal organism are the even-chain fatty acids. The proof of the above 

 statement is based upon experimental feeding of fatty acids to diabetic or 

 fasting rats or to dogs, upon liver perfusion tests, chiefly with dogs, and 

 upon experiments with tissue slices. 



Butts and collaborators^^ demonstrated that butyric, caproic, and 

 caprylic acids, when fed as their sodium salts, were excreted as acetone 

 bodies when administered to fasting rats; on the other hand, practically no 



2" H. J. Deuel, Jr., and M. GuUck, J. Biol. Chem., 96, 25-34 (1932). 



