60 Report or DEPARTMENT oF ANIMAL HosBANDRY. 
The foregoing figures are instructive in showing approxi- 
mately how the energy of the rations was utilized by these two 
milch cows. After accounting for the energy of maintenance on 
the basis of the best known data, viz: 18,000 Calories for an 
animal weighing 500 kilos (1100 Ibs.) and the energy of the milk 
solids, we have a balance amounting on the average to about 
one-quarter of the available energy of the ration. If the ration 
were diminished to the extent of this balance it would certainly 
result in a lessened milk yield, consequently we are justified in 
concluding that this balance has some necessary function or 
relation in milk secretion. 
The most natural and logical conclusion is that in part at 
least it sustains the work of milk secretion, i. e., the vital 
activity involved in the metabolic changes occurring in the milk 
glands or elsewhere in the formation of milk solids. There is, 
of course, more work demanded for mastication and digestion 
than is the case with the much smaller maintenance ration. 
Nevertheless it is fair to regard the milch cow as a working 
animal, not in the exercise of mechanical force but in the main- 
tenance of manufacturing processes which are sustained by the 
application of the quiet energies of life, 
