2s"ew York Agricultural Experiment Station. 53 



energy values and relations. 



As before stated, the main object of these experiments was to 

 srudy 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. 



3l€tJwds. — Daily samples of the fresh foods, excreta and milk 

 were selected with great care. The samples of fresh fOiPds and 

 feces were dried down over steam coils at a temperature of 

 about 60° C. The urine and milk samples to v»hich formalde- 

 hyde 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 oi 

 nitrogen during the drying. Xitrogen 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. N lost x 5..34.3 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. ^Yith 

 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. 



