May, 1929] FOODS IN A COLLEGE COMMUNITY 57 



tion Laboratory and its extensive practical use in our research at 

 the New Hampshire Agricultural Experiment Station demonstrate 

 that it is now possible to determine the energy value both of the 

 modern diet and of feces accurately and in much less time than is 

 x'equired in the use of the complicated bomb calorimeter. 



The technique of the oxy-calorimeter requires two simple pro- 

 cedures, the drying of the sample of food or feces to an air-dry con- 

 dition and the burning of the air-dry sample in the apparatus. The 

 latter procedure requires only 15 minutes at most, and experience 

 in the burning of samples can be readily acquired. An individual 

 whose energy intake is to be studied can easily cooperate with the 

 clinician or dietitian in securing the air-dry sample of his food by 

 placing in a previously weighed pan a duplicate of each serving of 

 food eaten during the day. At the end of the day the pan will con- 

 tain a duplicate of the total food intake. If extreme accuracy is 

 required, the weight of the food eaten should be known and an 

 equivalent weight placed in the pan. But if a serving of food seem- 

 ingly similar to the serving eaten is placed in the dish, the error in- 

 volved is for most purposes insignificant. In a large dietary study of 

 twelve men voluntarily undergoing a period of undernutrition,! du- 

 plicate samples of the food served to the twelve men were placed 

 in two extra dishes on the table, termed the "thirteenth and the 

 fourteenth men." The agreement between these two samples was 

 all that could be expected, and this method of sampling the day's food 

 intake was considered satisfactory. 



Examination of the data secured in our research with the oxy- 

 calorimeter suggests that in the case of mixed meals, at least, the 

 energy value may be estimated by an even simpler means than the 

 use of the oxy-calorimeter. With the individual food items such as 

 doughnuts, candy, ice cream, and the like, the ratio between the 

 energy content and the weight of air-dry matter was often found to 

 vary rather widely. But with the mixed meals the ratio was re- 

 markably constant, 5 calories per gram of air-dry matter on the 

 average. In view of the high digestibility of the foods consumed by 

 man, it is clear that by determining the air-dry weight in grams of a 

 mixture of foods and by multiplying this weight by the factor 5, one 

 can estimate the total calories in a mixed meal with a relatively high 

 degree of accuracy. This procedure does away with the necessity 

 for using either the bomb or the oxy-calorimeter, and although it 

 cannot have the scientific accuracy of either of these rigidly tested 

 means of energy measurement, nevertheless we believe that as a pro- 

 cedure in the hospital and in the dietetic laboratory it is of great 

 practical value. 



In the tabular presentation of our data emphasis has been laid 

 upon the calories and the protein which may be purchased for ten 



(1) Benedict, P. G., W. R. Miles, P. Roth, and H. M. Smith, Carnegie 

 Inst. Wash. Pub. No. 280, 1919, p. 68. 



