50 REPORT OF DEPARTMENT OF ANIMAL HUSBANDRY OF THE 
this demand ina givencase. For instance, during her maximum 
production the milk of Cow 12 contained about 1.12 lbs. of pro- 
tein (N x 6.25) daily. The cow was eating each day 2.6 lbs. of 
digestible protein. The real question is, What is the function 
of the protein remaining after deducting the milk protein from 
the total amount eaten, or in this case, 1.48 lbs.? An examina- 
tion of the figures for urine nitrogen shows that the larger part 
of this balance, or 1.2 lbs., was not stored but was broken down 
into simpler compounds and so destroyed. Does this metabolic 
change bear any fixed relation to the milk solids or milk fat 
secreted? The data of these experiments indicate a negative 
answer to this question. 
