51 



flour and the other grades in this respect. The digestibility of all 

 these flours was found to be high, apparently owing largely to their 

 mechanical condition, that is, owing to the fact that they were tinely 



ground. 



Microscopical studies of the feces from bread made from the different 

 grades of flour indicate that the superior digestibility of patent-flour 

 bread is due to the flneness of division of the flour particles and also to 

 the fact that the cell walls of the material making up the interior of 

 the wheat berry are less resistant to digestive juices than the walls of 

 the cells making up the outer layers of the grain. In other words, the 

 patent flour is superior as regards digestibility, on account of both its 

 mechanical condition and its physical properties. 



In discussions of the comparative value of fine wheat flour and the 

 coarser grades, it is often claimed that the larger proportion of mineral 

 matter, and especialh' phosphorous compounds, in whole-wheat and 

 graham flours is a reason for preferring them to patent flour. In this 

 case also it is undoubtedly true that the proportion of mineral con- 

 stituents which is digestible, or, in other words, which the body can 

 retain, from the diflerent sorts of flour, must be considered, as 

 well as the amounts which chemical anabasis shows to be present in 

 the food. In view of the fact that there is apparently no satisfac- 

 tory method for determining the proportion of ash in the feces, 

 derived from metabolic products, and that it is, therefore, impossible 

 by present methods to determine the true digestibility of the mineral 

 constituents, no values for the digestibility of ash have been included 

 in the present bulletin. It ma}" be noted in this connection that 

 it is a well- recognized fact that when the coarser milling products 

 are fed to cattle no great amount of phosphorus (one of the most 

 important manurial elements) is retained in the animal body. This may 

 possibly be an indication that the phosphorus, even if present in con- 

 siderable amounts in the feed, is not in a form which can be assimilated 

 by animals. This is, however, little more than conjecture, and more 

 experiments with man and the lower animals are needed before satis- 

 factory conclusions can be drawn. 



Briefly stated, the most important deductions from the results of 

 these investigations with hard and soft wheat are in accord with the 

 conclusions drawn from the earlier investigations of this series. The 

 nutritive value of flour, in so far as the quantities of digestible protein, 

 fats, and carbohydrates, and available energy are concerned, is not 

 increased by milling the wheat in such a way as to retain a large pro- 

 portion of bran and germ. The differences in the amounts of total 

 nutrients furnished the body by the various grades of flour are, how- 

 ever, relatively small, all grades being quite thoroughly digested. 

 The coarser flours have a tendency to increase peristaltic action, and 

 are on this account especially valuable for some persons. Judged by 



