89 



the lower protein content, the differences in the present instimce being 

 even more pronounced than those in the earlier experiments. In both 

 cases, then, the indications are that the widening of the ratio of protein 

 to starch in the Hour lowers the digestibility of the protein. 



As mentioned before, the differences in digestibility of the carbohy- 

 drates of the same grade of Hour from the two lots of wheat were 

 small, being largest in the case of the entire-wheat and Graham flours. 

 In the case of the straight-grade tlours 98,2 per cent of the carbohy- 

 drates from the Oregon wheat and 97.7 per cent from the Oklahoma 

 wheat were digested. Since the carboh\drates of wheat flour are com- 

 posed largely of starch, it is evident that wheat starch is a highly 

 digestible nutrient, and more thoroughly digested in the form of 

 straight-grade than in the other flours. The average difference in the 

 digestibility of the carbohvdrates of the breads made from the Graham 

 and straight-grade flours amounts to 8.7 per cent in favor of the 

 straight-grade flour. 



UNDIGESTED STARCH IN FECES. 



In former reports it was pointed out that the large particles 

 observed in the fecal matter from the Graham and entire-wheat flours 

 contained unaltered wheat-starch granules, which had escaped com- 

 plete digestion. In the present digestion experiments also, microscopic 

 studies showed the presence of unaltered starch grains in the feces 

 from the Graham and entire-wheat flours. 



EXPERIMENTS WITH BREAD FROM "BRAN FLOUR." 



As pointed out in the preceding experiments in the present bulletin 

 and in similar experiments previously reported, the Graham flour which 

 contains the whole of the wheat kernel, including the bran, and is more 

 coarsely groiuid than entire-wheat or standard patent flours, is less 

 digestible than either of these two grades. The cause of this differ- 

 ence has sometimes been attributed to the coarseness of the brann}' 

 particles. In order to determine what influence bran in a fine state of 

 division would have upon the completeness of digestion, three experi- 

 ments were made with straight-grade flour to which ver^- flnely ground 

 bran was added. For convenience this material has been designated 

 '•bran flour." 



This bran flour was prepared from milling products of Oklahoma 

 wheat, described on pages 12 and 13. A (luantity of the bran (No. 1:13) 

 was ground in a burr mill and then in a Maerker mill until it was very 

 tine. Some of the ground bran was then mixed with straight-grade 

 flour (No, 276), the quantity of bran in the mixture (No. 415) being 14 

 per cent of the total, which was about the proportion of bran removed 

 in milling. Bread was made from this modifled flour in the same way 



