New Yokk AoKicrLTUKAL Experiment Station. 495 



(4) The observation through this entire long period of time 

 of such data as would enable the experimenter to keep nitrogen 

 and fat balances, which of necessity would include a determina- 

 tion of the urea nitrogen or the amount of" metabolized protein. 



THE PLAN, MATERIALS AND PROCEDURE OF THE 

 EXPERIMENT. 



During the past year an attempt was made at this Station, with 

 a gratifying degree of success, to conduct an experiment in ac- 

 cordance with the conditions previously outlined, the main object 

 of which was to discover the necessary relation which may exist 

 between any class of compounds in the food and the production 

 of milk fat. 



The Plan of the Experiment. 



The plan of the experiment, as finally executed, involved the 

 following: 



(1) The feeding of normal foods for a period of about two 

 weeks, followed by the same foods from which the fats had been 

 extracted during ninety-five days, all of which were weighed and 

 analyzed especially for nitrogen and fats. 



(2) Changes in the rations from a minimum of 15 lbs. of air- 

 dry food to a maximum of 22| lbs., and from a minimum of 1.3 

 lbs. of total protein to a maximuim of 3.06 lbs. These changes 

 were so arranged that during a certain period a decrease of pro- 

 tein was accompanied by an increase of carbohydrates. 



(3) The analysis of the milk for one hundred and two days. 



(4) The collection and analysis of the urine and feces from the 

 experimental animal for sixty-six days, this being done continu- 

 onsly during fifty-nine days of the time in which extracted foods 

 were fed. 



(5) A study of the distribution of certain mineral constituents 

 of the food in the milk, urine and feces. (Incidental and not com- 

 pleted.) 



(6) A study of the distribution of the energy of the food in 

 the milk, urine and feces. (Incidental and not completed.) 



