New York AGRICULTURAL EXPPRIMENT STATION, 53 
ENERGY VALUES AND RELATIONS. 
As before stated, the main object of these experiments was to 
study the food sources of milk fat.. The complete record of the 
foods eaten, of the excreta and of the milk produced for so long 
a time, and the collection and preservation of samples of all of 
these, enabled us to study with advantage certain other ques- 
tions related to animal nutrition. Attention was given chiefly 
to energy values and relations, although an unsuccessful 
attempt was made to study sulphur metabolism. 
The plan of work was the usual one, and the only one possible 
without the aid of the respiration calorimeter, viz: the deter- 
mination in a calorimeter (Berthelot-Atwater) of the heats of 
combustion of the foods, milk and excreta of two cows during 
several periods of time. The data thus secured have made pos- 
sible a calculation of energy values and uses, the figures from 
which are not without interest. 
Methods.—Daily samples of the fresh foods, excreta and milk 
were selected with great care. The samples of fresh foods and 
feces were dried down over steam coils at a temperature of 
about 60° C. The urine and milk samples to which formalde- 
liyde had been added were stored in tightly closed fruit-jars, and 
in this condition remained apparently unchanged for a long time. 
The quantity of formaldehyde used was about 2 ¢c.c. to one quart 
of liquid. 
The calorimeter determinations were made in the usual way. 
The milk and urine were dried down in the capsules in which 
they were burned. The urine suffered more or less loss or 
nitrogen during the drying. Nitrogen determinations were made 
in samples of urine before and after dessication and the amount 
of nitrogen lost by drying was assumed to come wholly from 
urea. WN lost x 5.843 Cal. would therefore be the loss of energy 
due to drying and the number of calories thus calculated was 
applied as a correction to the calorimeter determinations. With 
those samples of urine which had suffered no fermentative 
changes this correction was in many instances less than one 
small calorie per gram of urine and never much over two small 
calories. 
