NUTRITION INVESTIGATIONS. 469 



standard patent flours milled from the same lot of hard Scotch Fife 

 spring wheat, the graham flour contained the highest and the patent 

 flour the lowest percentage of total protein. But according to the 

 results of digestion experiments with these flours the proportions of 

 digestible or available protein and available energy in the patent flour 

 were larger than in either the entire-wheat or the graham flour. The 

 lower digestibility of the protein of the latter is due to the fact that in 

 both these flours a considerable portion of this constituent is contained 

 in the coarser particles (bran), and so resists the action of the digestive 

 juices and escapes digestion. Thus while there actually may be more 

 protein in a given amount of graham or entire- wheat flour than in the 

 same weight of patent flour from the same wheat, the body obtains less 

 of the protein and energy from the coarse flour than it does from the 

 fine, because, although the including of the bran and germ increases the 

 percentage of protein, it decreases its digestibility. By digestibility 

 is meant the difference between the amounts of the several nutrients 

 consumed and the amount excreted in the feces. 



The digestibility of first and second patent flours was not appreciably 

 different from that of standard patent flour. The degree of digesti- 

 bility of all of these flours is high, due largely to their mechanical 

 condition — that is, to the fact that they are finely ground. 



These results are in accord with other accurate investigations, but 

 their especial value lies in the fact that the experimental inquiry has 

 been more thorough and extensive than any previously reported. The 

 disparity between the conclusions just quoted and much of the popular 

 belief, current newspaper statements, and, indeed, some of the teach- 

 ing in physiological text-books, illustrates the importance of having 

 such problems carefully studied. 



METABOLISM EXPERIMENTS WITH THE RESPIRATION CALO- 

 RIMETER. 



From the more purely scientific standpoint, the interest of this nutri- 

 tion inquiry culminates in the experiments with the respiration calo- 

 rimeter. These have for their object the study of the transformations 

 of matter and energy in the living organism. In other words, they rep- 

 resent an inquiry into the most fundamental and most important laws 

 of nutrition. The apparatus used for the purpose is the Atwater-Rosa 

 respiration calorimeter described on page 447. 



The most important result thus far obtained by the use of this appa- 

 ratus is what amounts practically to a demonstration that the law of the 

 conservation of energy applies to the living organism. It has long been 

 known that this law obtains in the inorganic world. The proof that 

 this law obtains in the inorganic world was one of the great scientific 

 achievements of the last century. It has, of course, been assumed 

 and very generally believed that it must apply in the organic world, 

 in the living being also, but a complete and satisfactory demonstration 

 has not hitherto been made, although an approximation was found in 



