256 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Table 11. — Summary of coefficients of availability of nutrients and energy in preliminary and calorimeter periods and with 



ordinary and alcohol diet. 



Exp( rimi nts with E. 0. 



< (rdinary diet, average 6 experiments 



Alcohol diet, average o experiments- 



Preliminary period, average L2 experiments 

 Calorimeter period, average 12 experiments. 



Experiments with ■/. F. S. 



Ordinary diet, average 6 experiments 



Alcohol diet, averages experiments 



Preliminary period, average 4 experiments 



Calorimeter period, average 4 experiment.- 



Average 12 experiments with ordinary food- 

 Average 8 experiments with alcohol 



Average 16 preliminary periods 



Average 16 calorimeter periods 



DISCUSSION OF THE RESULTS OF THE EXPERIMENTS. 



The .special purpose of the experiments summarized on the preceding pages, in so far as they 

 have had to do with the nutritive action of alcohol, has been the study of the metabolism of the 

 energy of alcohol and its consequent value for fuel as compared with isodynamic amounts of 

 carbohydrates and fats. Incidentally, its effects upon digestion, the completeness of its oxida- 

 tion, and its action in protecting body fat and protein from oxidation have also been observed. 

 The more important results may be discussed under the following topics: 



1. Effect of alcohol upon the digestion of food. 



2. Proportions of alcohol oxidized and unoxidized. 



3. Metabolism of the energy of alcohol. 



4. Protection of body material by alcohol. 



". Protection of body fat. 

 Ji, Protection of body protein. 



5. Effect of alcohol upon the radiation of heat from the body. 

 ti. Alcohol as a source of heat in the body. 



7. Alcohol as a source of muscular energy. 



EFFECT OF ALCOHOL UPON THE DIGESTION OF FOOD.— DIGESTIBILITY VERSUS AVAIL- 

 ABILITY OF NUTRIENTS. 



The term digestibility as applied to food has several meanings, which are not clearly distin- 

 guished in popular usage. It commonly refers to either the ease with which a given food 

 material is digested, or the time required for the process, or the extent to which the material 

 "agrees v or "disagrees" with different persons, or its effects upon bodily comfort and health. 

 These factors depend largely upon individual peculiarities, vary widely with different persons and 

 with the character of the food, and are difficult to measure. 



The term digestibility is also used to designate the quantity or proportion of the food or of 

 each of its different ingredients — protein, fats, carbohydrates, and mineral matters — actually 

 digested and absorbed in the passage of the food through thedigestive tract. Only this latter factor 

 of digestibility is considered in these experiments. To determine what amount of each nutrient is 

 actually digested it is necessary to know the quantity that is taken into the body in food and the 

 quantity that has escaped digestion and is excreted in the feces. The latter quantity is not easily 

 determined, however, because the feces contain, besides those portions of the food that have 



