MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



257 



resisted the action of the digestive juice.-., other materials, the so-called metabolic products, 

 which arc mainly the residues of the digestive juices, and which arc not easily separated from 

 the undigested portion of the food. For this reason it is difficult to determine theactual digesti- 

 bility of food or of its several ingredients. 



The availability of the fond or of the several ingredients, however, may he more accurately 

 determined. By availability is here meant the quantity or proportion that can he used for the 

 building and repair of tissue and the yielding of energy. The metabolic products, although derived 

 originally from the digested food, are not used for either building material or fuel, and hence 

 are not available in the sense in winch the word i> here employed. They may. therefore, be 

 included with tin 1 undigested residue of the food and the small quantities of intestinal epithelium 

 and other materials which make up the rest of the feces, and the amounts of available nutrients 

 may be found by subtracting from the total ingredients of the food the total corresponding 

 ingredients in the feces. These have often been called the digestible rather than the available 

 nutrients, hut the distinction here made is quite important. 



The availability of the ingredients as thus determined is usually expressed by the percentage 

 of the total amount of each in the food. This percentage is called the coefficient of availability. 

 In the following table, which is a summary of a more detailed table given in the Appendix, the 

 coefficients of availability of the protein, fats, and carbohydrates of the ordinary diet are 

 compared with those of the alcohol diet, as actually found in the experiments. The average 

 coefficients of availability of the nutrient- of food as found in 93 experiments* with health} men 

 with ordinary diet under various conditions of work and rest are appended in the table for 

 comparison. 



Table 12. — Coefficit nts of availability of food in tin an rages of expi rinu nts with and without alcohol. 



Kind ami number of experiments. 



St i nts of availability. 



Protein. 



Experiments mun directly comparable. 



Without alcohol, Nos. 9, 11, 26 and 28,29 ami 31,32 and 34 

 With ale. ill. .1, Nos. 10,12,27,31,33 



I'.ijii rimenls less directly comparable. 



Without alcohol, Nos. 5, and 13 and 14 



With alcohol, Nos. 7 and 15 to 17 



A verage i >f other observations 



/'. r " "' 

 ill', li 

 93.7 



92.6 



'.i.-,. (i 

 '13.11 



/'. r a nt. 

 94.9 

 94.6 



94. 1 

 94.4 

 95.0 



Carbohy- 

 drates. 



/'' r ci nt. 

 97.9 



98.1 

 97. 3 

 98.0 



Energy. 



/'' i ct nt. 



91. S 



92. 1 



90.3 

 91.3 



■ 92. 3 



' Availability of energy based upon average proportions and amounts of nutrients found in dietaries of 38 

 families of farmers, mechanics, ami professional men ami 15 col lege boarding clubs in different parts of the United 

 States. See article by A. P. Bryant on "Some Results of Dietary Studies." Yearbook U. S. Dept. Agriculture, 

 L898, p. 439. 



It thus appears that the alcohol had little appreciable effect upon the availability of the other 

 ingredients of the diet; the coefficients of availability of the nutrients of the ordinary food 

 were practically the same with and without alcohol as part of the diet. The protein appears to 

 have been slightly more available when the diet contained alcohol. The differences, especially in 

 the more comparable experiments, are less than might be found with different subjects using the 

 same ordinary food, or with the same subject using the same food at different times and under 

 different conditions. 



The conclusion from the results of these experiments would be to the effect that alcohol in 

 moderate amounts tended to increase very slightly the availability of the nutrients of the diet, 

 especially of the protein. In view, however, of the fact that there are often marked differences 

 in the availability of the same diet with different persons and with the same person at different 



See Atwater and Bryant, Availability and Fuel Value of Food Materials, Kept. Storrs (Conn.) Expt. Sta., 

 1899, p. 73. 



