8 



made 'with the different kinds of flour. Wheat ranges in protein con- 

 tent from about 11 to 17 per cent; therefore, in order that the results of 

 experiments may be comparable, the three kinds of flour should be 

 milled from the same lot of wheat. In the former report it was shown 

 that when the three different kinds of flour were ground from the same 

 lot of hard spring wheat the graham and entire-wheat flours contained 

 a little more protein and gave a slightly higher fuel value than the 

 straight patent flour; but the coarser graham and entire-wheat flours 

 had a lower coefiicient of digestibility than the flner straight patent 

 flour. Hence the straight patent flour furnished the bod}' more 

 nutritive material per gram or per pound than either the graham or 

 entire-wheat flour. Because of the importance of the subject and the 

 extensive use of wheat as a human food it was deemed desirable to 

 repeat the work, and in so doing to extend the periods of the digestion 

 experiments over a longer time than in the case of the experiments 

 previously reported, in which they were only two da3's each. The 

 experiments of 1900-1901 were therefore practically a repetition of 

 those of 1899-1900, except that the digestion period in each case was 

 twice as long, i. e., four days. 



In 1901-2 experiments were made similar to those of 1900-1901, but 

 with soft winter wheat, which is somewhat difierent in character from 

 the hard spring wheat, in order to determine whether the results would 

 be the same with flours ground from different sorts of wheat. 



In connection with both series of experiments a num})er of analyses 

 were made of the varieties of wheat studied and of their milling products 

 as well as of the milk which formed a part of the diet in the digestion 

 experiments. The necessary' anal3^ses were also made of the feces and 

 urine to secure data for use in computing the digestibility of the food 

 and the balance of income and outgo of nitrogen. 



METHODS OF SAMPLING AND ANALYSIS. 



The analytical methods employed in these investigations were prac- 

 tically those recommended by the Association of Official Agricultural 

 Chemists," a few modifications suggested b}^ experience being intro- 

 duced. 



A sample of each loaf of bread used during the separate digestion 

 experiments was analyzed. One hundred grams of bread was reserved 

 for the dry matter determination, and proportional parts of the dry 

 matter of the bread from various loaves were united to form a com- 

 posite sample, which contained a part of each loaf of bread propor- 

 tioned to the size and moisture content of the loaf. 



A composite sample was made of the milk in the experiments of 

 1900-1901 by saving, in a bottle containing 100 milligrams of potas- 



« U. S. Dept. Agr., Division of Chemistry Bui. 46, revised. 



