THE RELATIONS OF METABOLISM TO FOOD-SUPPLY. 145 
food fat and body fat, but it is most natural to suppose that the re- 
sorbed fat of the food, being already in circulation in the body, is 
more easily accessible to the active cells than the stored-up fat of 
the adipose tissue and is, therefore, metabolized in preference to the 
latter. 
Rubner,* in his study of the replacement values of the several 
nutrients, has demonstrated the same effect of food fat. Fat 
supplied in the food is utilized as a source of energy to the body and 
a corresponding quantity of body fat escapes oxidation, while if 
supplied in excess fat is stored up in the body. The experiments 
were made in the same manner and are computed on the same 
assumptions as those upon proteids recorded on p. 106. All were 
on dogs except the third, which was on a rabbit. 
Total Nitrogen Fat Gain or Loss 
Food. of Excreta, Metabolized, of Fat, 
Qrms. Grms. Grms. 
Nothing 2... cc cee eae nee 1.69 60.47 — 60.47 
200 grms. bacon............. 1.68 71.80 +128 .20 
Nothing: .. : dans vaees Reo Seles 2.14 33.78 — 33.78 
39.75 grms. of butter fat..... 2.44 33.48 + 6.27 
NOthing say anaes wie tw capes 0.778 7.18 — 7.18 
26.1 grms. bacon7.......... 1.045 6.44 + 19.63 
Nothing's ci gah sate vcs as aie) oa 2.56 42.40 — 42.40 
100 grms. fat............---- 2.48 47.73 + 52.27 
Nothing: 3. scat cones neces 1.08 22.88 — 22.88 
40 grms. bacon............-. 1.32 28.73 + 11.27 
In nearly every case there was a slight increase in the proteid 
metabolism, as in Pettenkofer & Voit’s experiments, and a some- 
what greater, although still not very considerable, increase in the 
fat metabolism. In the main, however, the food fat was metabolized 
in place of the body fat. 
In those of Pettenkofer & Voit’s experiments in which fat was 
added to an insufficient ration of meat the same effect was pro- 
duced, as appears when we compare the results upon a ration of meat 
* Zeit. f. Biol., 19, 328-334; 30, 123. 
{ Results approximate only. 
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