DR. H. P. ARMSJBY'S EXPERIMENTS 305 



erns value. Dr. H. P. Armsby's experiments show 

 the following results: "Of the total or 'gross' energy 

 of hay, about 41 per cent was capable of conversion 

 into the kinetic form in the animal, while the remain- 

 ing 56 per cent was found as potential energy in the 

 excreta. Of the 44 per cent which I have called metabo- 

 lizable energy, about 63 per cent, equivalent to 27.72 

 per cent of the gross energy of the hay, was found to 

 be available for the maintenance of the animal, while 

 the remaining 37 per cent of the metabolizable 

 energy, under our conditions of experiment, simply 

 went to increase the heat -production of the animal. 

 This 37 per cent of the metabolizable energy seems 

 to represent the expenditure of energy which is in- 

 volved in making the remaining 63 per cent available 

 for the actual uses of the organism. The above results 

 represent the average of four experiments only, on a 

 single animal, and of course should be generalized 

 from very cautiously." 



The more concentrated the food is, within proper 

 limits, the less per cent of energy is needed to make it 

 available. This fact explains in part why animals 

 cannot be sustained and produce sufficient energy for 

 growth and work on unconcentrated food, difficult to 

 masticate and prepare for assimilation. It is because 

 too great a per cent of the energy of the food is used 

 in its preparation by the stomach, hence the net 

 energy is small. 



When horses are doing light work or are idle, not 

 only will less food suffice, but the proportion of rough, 

 cheap food to the concentrated may be increased. 



