SOURCES OF FAT IN ANIMAL BODY 547 



and Meissl and Strohmer, 106 reported that, although all the nitrogen of the 

 protein fed was excreted in the urine, an appreciable amount of the carbon 

 ingested as protein failed to be accounted for in the urine or expired air, 

 and must therefore have been converted to fat and stored in that form. 

 The quantity of carbon retained was of such magnitude as to preclude its 

 storage exclusively as carbohydrate. 



In calculating the carbon content of the protein, in their original studies, 

 Pettenkofer and Voit 149 - 150 had used the factor 3.68 for the C:N ratio. 

 However, Rubner 151 showed that the above factor was too high when it 

 was determined on meat completely extracted with ether; according to the 

 latter investigator, the figure for the C : N ratio in meat protein should be 

 3.28 : 1. When the new factor was used for the calculation of carbon reten- 

 tion in the original Pettenkofer-Voit experiments, the carbon retained was 

 very small, or amounted to zero. On this basis, Pfliiger 152 wrote his 

 polemic refutation of this proof of transformation of protein to fat. 



Table 4 



Comparison of the Potential Glycogen Formation from Protein Carbon 



Retained by a Cat Receiving Lean Meat over an 8-Day Period with That 



Actually Found on Analysis 



Total per day Total for 8 days 



Category N C N C 



1. Protein metabolized (from urinary N) 13.0 41. 6 6 104.0 332. 8 6 



2. Carbon excreted 



a. Urine — 7.5 60.0 



b. Feces — 1.4 11.2 



c. Respiration — 25.4 203.2 



d. Total — 34.3 274.4 



8. Carbon retained (1 - 2d) — 7.3 58. 4 



4 . Glycogen equivalent (3/0.444 ) c — 16.4 131 . 5 



5 . Glycogen found — — 35 . 



a Data adapted from M. Cremer, Munch, med. Wochschr., 44, 811 (1897); Z. Biol., 

 38, 309-314 (1899). 



6 Calculated on a C:N ratio of 3.2: 1. 



c Based on a value of 44.4% carbon in glycogen. 



However, the subsequent results of Cremer 153 can be interpreted as 

 offering proof of the intercon version of protein and fat. After removal of 

 much of the storage fat from a cat by a fast continuing over a number of 



151 M. Rubner, Z. Biol., 21 [n.s. 3], 250-334 (1885). 



152 E. Pfliiger, Arch. ges. Physiol. (Pfliiger's), 52, 239-322 (1892). 



183 M. Cremer, Munch, med. Wochschr., 44, 811 (1897); Z. Biol, 38 [n.s. 20], 309-314 

 (1899). 



