644 Journal of Agricultural Research Vol. vi, No. 17 



As regards the experimental details, the methods followed in studying 

 the hard palates were similar to those previously reported with other 

 foods. 1 As no attempt was made to maintain body weight or to approxi- 

 mate a nitrogen equilibrium, the quantity of the entire ration to be 

 eaten was not stipulated. The feces occurring from each experimental 

 period, as indicated by charcoal markers, were collected and dried to 

 remove the water. Samples of foods eaten were retained for analysis 

 and all analyses of foods and feces were made by the methods described 

 by the Association of Official Agricultural Chemists. 2 



In order to determine the digestibility of a single food contained in a 

 mixed diet, it is necessary either to determine the digestibility of the 

 basal ration and to apply the proper correction to the values obtained 

 for the digestibility of the total diet, or to estimate the undigested 

 residue occurring from the various constituents of the diet by means of 

 coefficients previously determined, and to make proper allowance for 

 this undigested material. The latter method has been followed in this 

 instance and the method of estimating the digestibility of the protein 

 of the meat loaf alone is indicated by the following equations : 



[Weight of protein in potato, crackers, and butter] X [Percentage of 



undigested protein occurring in each] = [Weight of undigested 



protein present in feces derived from basal ration]. 

 [Total undigested protein in feces] — [Undigested protein in feces 



from basal ration] = [Undigested protein occurring from meat 



loaf]. 

 [(Total protein of meat loaf )— (Undigested protein from meat 



loaf)] -f- [Total protein of meat loaf ] = [Estimated percentage 



digestibility of meat loaf alone]. 

 On the basis of determinations by previous investigators the coef- 

 ficients assumed in these equations for the digestibility of the protein of 

 the potatoes, crackers, and butter are 83 per cent, 3 93.8 per cent, 4 and 

 97 per cent, 3 respectively. 



In Table I are recorded the essential experimental data of the digestion 

 experiments with hard palates, including the total weight of food eaten, 

 the nutrients furnished, the weight of feces, the undigested nutrients 

 therein, the percentage of the different nutrients digested, and the esti- 

 mated digestibility of the protein of the meat loaf. 



1 Langworthy, C F., and Holmes, A. D. Digestibility of some animal fats. U. S. Dept. Agr. Bui. 310, 

 22 p. 1915. 



2 Wiley, H. W. Official and provisional methods of analysis, Association of Official Agricultural Chem- 

 ists. As compiled by the committee on revision of methods. U. S. Dept. Agr. Bur. Chem. Bui. 107 (rev.), 

 272 p., 13 fig. 1908. Reprinted in 1912. 



8 Atwater, W. O., and Bryant, A. P. The availability and fuel value of food materials. InCorm. Storrs 

 Agr. Exp. Sta. 12th Ann. Rpt., 1899, p. 104. 1900. 



* Woods, C. D., and Merrill, L. H. Studies on the digestibility and nutritive value of bread at the Maine 

 agricultural experiment station, 1899-1903. U. S. Dept. Agr. Office Exp. Stas. Bui. 143, p. 33. 1904. 



