1004 



ANNUAL, REPORT OF THE 



Off. Doc. 



it convt'js tile idcji that a pai-ticular food "agrees'' wilh the user, 

 i. e., that it does not cause distress when eaten. The term is also 

 \(n-j commonl}- understood to mean Ihe ease or rapidity of dij^es- 

 tion, and one food is often said to be more digestible than another 

 because it is digested in less time. However, the term digestibility 

 is most commonly understood in scientific treatises on the subject 

 to mean thoroughness of digestion. The digestibility of any food 

 may be learned most satisfactorily by oxperiinents with man, al- 

 though experiments are also made by methods of artificial diges- 

 tion. In the experiments with man both food and feces are an- 

 alyzed. Deducting the amounts of the several nutrients in the feces 

 from the total amounts of each nutrient consumed shows how 

 much of each was digested. The results are usually expressed 

 in percentages and spoken of coefficients of digestibility. From a 

 large number of experiments with man it has been calculated that 

 on an average the different groups into which foods may for con- 

 venience be divided have the following coefficients of digestibility: 



Coefficients of Digestibility of Different Grou])s of Foods. 



P4 



(1) c 



Animal foods, 



Cereals and sugars, . . 

 Vegetables and fruits, 



75 



75 

 75 



Making use of these figures, the digestible nutrients furnished by 

 any food may be readily cahmlated. Thus, as shown by the table 

 on composition above, sirloin steak contains 1G.5 per cent, protein. 

 One and one-half pounds would, therefore, contains 0.2475 pound 

 protein, or in round numbers, 0.25 pound (t.5x 16.5 = 0.2475). As 

 shown by the coefficients of digestibility quoted above, 98 per cent, 

 of the protein of animal food is digestible. Therefore, 1.5 pounds 

 sirloin steak would furnish 0.245 pound digestible protein (0.25 x 

 O.OS = 0.245). The digestibility of the several nutrients in a given 

 quantity of any food may bo calculated in a similar way. 



