226 IV. CONVERSION OF FAT TO CARBOHYDRATE 



3C16H32O2 + 2IO2 > SCeHisOe 



Palmitic acid Glucose 



Illustrating the Theoretical Conversion of Palmitic Acid to Glucose as Postidated by 



Lusk2 



Thus, the greater the proportion of the total metabohsm which is con- 

 cerned with the fat -> carbohydrate change, the lower would be the ex- 

 pected non-protein R.Q.^ 



In a number of reports on the R.Q. of animals, values lower than the 

 theoretical minimum of 0.707 for the non-protein R.Q. of fat have been ob- 

 served; the latter figure would be obtained when fat is the only non-protein 

 component being metabolized but in which its complete oxidation oc- 

 curs. 



Some of the experimental R.Q. values recorded are exceedingly low. 

 Thus, Pembrey^^ observed a figure of 0.55 in hibernating marmots, while 

 Voit^^ reported a minimum value of 0.33 during hibernation in this species. 

 In all of these experiments, the respiratory metabolism was at an extremely 

 low level, so that the actual carbon dioxide and oxygen measured represents 

 a very low quantity of the gases. Under these conditions, inaccuracies 

 might readily be traceable to analytical difficulties. Moreover, the respira- 

 tory exchange may not represent the true metabolic picture, inasmuch as 

 many of the hibernating animals exhibit Cheyne-Stokes respiration,^^ with 

 a consequent derangement of the acid-base balance of the blood. Another 

 suggestion is that such irregularities may be ascribed to differential changes 

 in solubility of carbon dioxide and oxygen which obtain in the colder blood 

 of the hibernating animal. ^^ The solubility of carbon dioxide would in- 

 crease to a greater extent than that of oxygen in the colder blood; this 

 would cause a greater retention of this gas, with a resultant lower R.Q. In 

 spite of all of these possibilities, Pembrey^^ reported that the R.Q. of active 

 marmots was 0.70 or higher. 



In addition to the analytical difficulty in determining respiratory gases in 

 hibernating animals, because of the small quantities of gases involved, it is 

 also true that most inaccuracies in gas analyses are due to an incorrect 

 determination of oxygen. When a closed circuit apparatus is employed, any 

 leak in the system will result in the calculation of an abnormally high value 

 for oxygen, with a resulting low R.Q. DuBois^^ listed over 100 low values 



" C. Voit, Z. Biol., 14, 57-160 (1878). 



8* E. Grafe, Die pathologische Physiologie des Gesa7nmtstoff- 2ind Kraflwechse's iei der 

 Ernahrung des Menschen. J. F. Bergmann, Munich, 1923; reprinted Ergeh. I'/itjsioI. 

 ^i, No. //, 1-499(1923). 



3* E. F. DuBois, Basal Metabolism in Health and Disease, Lea & Febiger, Philadelphia, 

 third ed., 1936, p. 280. 



