SOURCES OF FAT IN ANIMAL BODY 549 



tained material stored as fat. The results of Atkinson, Rapport, and 

 Lusk 154 indicate that, under the conditions of their experiments, the latter 

 situation existed. Table 5 gives a summary of the data upon which their 

 conclusions are based. 



Table 5 



The Respiratory Metabolism op Dog 18 Five Hours after the Feeding of 1000 



Grams of Meat" 



C0 2 , 2 , 



Category g. g. R.Q. Cal. 



/. Respiratory gases equivalent to 1.44 



g. nitrogen (urine) 6 13.46 12.23 0.802 38. 17 



2. Found in respiration 10. 10 8.72 0.842 



3. Respiratory gases equivalent in 



pabulum retained (1 - 2) 3.36 c 3.51 0.700 11. 32* 



4. Calories produced (calculated) in- 

 direct (1 - 3) — — 26.85 



5. Calories found (direct) — — — 27.52 



Adapted from H. V. Atkinson, D. Rapport, and G. Lusk, /. Biol. Chem., 53, 155-166 

 (1922); cited by G. Lusk, Science of Nutrition, 4th ed., Saunders, Philadelphia, 1928. 

 6 1 g. urinary nitrogen is equivalent to 9.35 g. C0 2 and 8.49 g. oxvgen. 

 e Equivalent to 0.92 g. carbon (3.36 X 12 / 4 4) or 1.2 g. fat (0.92/0.765). 

 d Obtained by multiplying fat carbon (0.92) by 12.32 Calories. 



Atkinson et al. 154 calculated that, had the retained carbon been stored as 

 carbohydrate, 2.3 g. of glucose would have been formed, with a caloric 

 equivalent of 8.63 Calories. Under these circumstances, the calories 

 calculated would have been 29.54 instead of 26.85 (based upon retention as 

 fat) compared with a value of 27.54 actually determined. These calcula- 

 tions further support the data from the respiratory quotient in indicating a 

 conversion of protein to fat. 



Lusk 110 refers to his findings published in 1906, in the first edition of his 

 book, in which he stated that 40% of the protein carbon which was capable 

 of conversion into glucose could be retained either as glycogen or as fat. 

 According to Williams, Riche, and Lusk, 155 this figure was indirectly shown 

 to be 33% while, according to the investigations of Atkinson, Rapport, and 

 Lusk, 154 50% of the potential glucose was deposited as fat. 



c. Proof of the Conversion of Proteins and Amino Acids to Fat, Based 

 upon the Formation of Carbohydrate. Although the direct demonstration 

 of the synthesis of fat arising from protein is a rather difficult one, the proof 

 of the conversion of protein to carbohydrate is relatively easy to obtain. 

 Since the transformation of carbohydrate to fat is likewise a readily demon- 

 strable change and one which is generally accepted, proof of the formation 



166 H. B. Williams, J. A. Riche, and G. Lusk, J. Biol. Chem., 12, 349-376 (1912). 



