Nov, 1931] FOODS IN A COLLEGE COMMUNITY 15 



millimeter length of stroke\ the temperature of the barrel of the pump 

 (which should not be touched with the hand), the prevailing atmos- 

 pheric pressure, and the assumption that the gas is completely saturated 

 with water vapor. The calculation may be expressed b.v the formula: 



^_(LxKXM)-o 

 W 



in which all the factors except L and Iv are the same as those described 

 for the formula on page 11. L is the total length of the full strokes 

 and any fraction of a stroke made with the pump, expressed in milli- 

 meters and obtained by multiplying the length of the pump stroke in 

 millimeters (as a rule precisely 200 mm.) bj- the total number of pump 

 strokes.' Iv is the number of cubic centimeters represented by each 

 millimeter length of stroke, based upon the internal diameter of the 

 pump. Since moist oxygen is introduced into the system, the factor M 

 is derived from Carpenter's standard tables^ for reduction of saturated 

 volumes, based upon the average temperature of the pump barrel and 

 the observed barometric pressure. The correction for nitrogen liberated 

 during the combustion is the same as explained on page 11. 



In one of the earlier descriptions of the oxy-calorimeter* it was 

 stated that the combustion chamber could likewise be attached to the 

 forms of respiration apparatus having the soda-lime container inside the 

 spirometer. We now question the advisability of using such forms of 

 respiration appai'atus for this purpose, since internal or external cooling 

 of these apparatus is impracticable. Combustions with such a set-up 

 will, however, give approximate energy values, and these types of res- 

 piration apparatus ma}^ be used with reasonable accuracy if a correction 

 factor is established by a standardization test with pure sugar. 



METHOD OF SAMPLING 



The sampling of edible waste of mixed meals and of individual 

 meals was carried out in the same manner as outlined in our earlier 

 report." In so far as possible all the edible waste of food that had been 

 prepared to serve at the table was collected. This collection did not 

 include kitchen refuse, inedible portions that would not be served on 

 the table, and uneaten foods such as butter that could subsequently be 

 used in cooking. It did, however, include both plate scrapings and the 

 edible waste of the cooked foods discarded in the kitchen. The plates 

 returned to the kitchen and the kitchen utensils were carefully scraped, 

 but undoubtedly a small amount of food material adhered to the plates 

 and to some of the cooking dishes and was not removed. Our calcula- 



^Computed from the length of the piston stroke, 200 mm., and the internal 

 diameter of the pump, usually about 48.5 mm.; corresponding to a volume of 

 1.848 c. c. per mm. length of stroke. 



^Not including the pumpful withdrawn temporarily to prevent undue expan- 

 sion of the bathing-cap at the moment of combustion and subsequently returned 

 to the apparatus. 



^Carpenter, T. M., loc. cit. 



^Benedict, F. G., and E. L. Fox, Journ. Biol. Chem., 1925, 66, p. 783. 



'Benedict and Farr, loc. cit. 



