18 BULLETIN 310, TJ. S. DEPARTMENT OF AGEICULTUEE. 



which are ordinarily designated as metabolic products. These 

 include residues of bacteria, digestive juices, internal secretions, and 

 epithelial cells of the stomach and intestines. Some of these products 

 of the body metabolism are soluble in ether and therefore occur in the 

 ether extract of the feces, together with the fat actually unavailable. 

 Moreover, these metabolic products are not derived necessarily from 

 the fat under consideration, but may be formed from protein and 

 carbohydrate as well, and probably are produced partly from food 

 eaten prior to the beginning of the experimental period. 



To determine either the amount or the percentage of fat actually 

 unutilized as distinguished from the total fecal fat (often called "un- 

 digested fat"), allowance must be made for fat in the fecal metabolic 

 products. The method adopted is not a direct one, since it is imprac- 

 tical to make the separation quantitatively, but is based on the 

 assumption that the quantity and quality of metabolic products 

 found depend on the nature and the amount of ingested food — that 

 the average percentage of metabolic products found in the ether 

 extract when the basal ration alone is eaten will be approximately 

 equal to that when the basal ration together with added fat is con- 

 sumed. 



Four experiments are herein reported with the basal ration with- 

 out added fat. The procedure was in no way different from that 

 employed in those tests in which large amounts of added fat were 

 eaten, the bulk of food in each series of experiments being approxi- 

 mately equal. The results of these tests are given below and 

 furnish a basis for calculating the necessary allowance for the meta- 

 bolic products contained in the ether extract of the feces. 



Data of digestion experiments with basal ration. 





Weight. 



Water. 



Protein. 



Fat. 



Carbo- 

 hydrates. 



Ash. 



Experiment No. 266, subject H. F. B.: 

 Blanc mange without added fat 



Grams. 

 2,307.0 



592. 

 1,392.0 



208.0 



Grams. 



1,296.8 



47.4 



1,211.0 



Grams. 

 45.4 

 65.1 

 13.9 



Grams. 

 14.5 

 17.8 



Grams. 

 939.0 

 449.9 

 167.1 

 208.0 



Grams. 

 11.3 

 11.8 



Fruit . 























4, 499. 

 136.0 



2, 555. 2 



124.4 

 38.9 

 85.5 



32.3 

 11.8 

 20.5 



1,764.0 



73.4 



1,690.6 



23.1 





11.9 







11.2 

















68.7 



63.5 



95.8 



48.5 











Experiment No. 267, subject D. G. G.: 

 Blanc mange without added fat 



1,922.0 

 335.0 



1,027.0 

 149.0 



1,080.4 



26.8 



893.5 



37.9 

 36.9 

 10.3 



12.1 

 10.0 



782.2 

 254.6 

 123.2 

 149.0 



9.4 

 6.7 



Fruit 























3,433.0 

 87.0 



2, 000. 7 



85.1 

 28.6 

 56.5 



22.1 



8.3 



13.8 



1,309.0 



42.2 



1,266.8 



16.1 





7.9 







8.2 











Per cent utilized 







66.4 



62.4 



96.8 



50.9 









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