Digestion Respiration Calorimetry Energy. 51 



which was replaced by new protein from this source. In all, 167.5 

 out of 263.1 therms in 100 Ibs. of gluten were lost either in the 

 urine or in carrying on the work of mastication, digestion, and 

 assimilation, leaving 95.6 therms which might be temporarily or 

 permanently stored in the body. This amount of protein was 

 available for building protein tissues or lean meat, which would 

 be its highest use, or it could serve for the production of body fat, 

 etc. 



72. Losses in undigested matter, methane, and urine. Studying 

 the lower division of the table we observe that if the total energy 

 of corn meal is placed at 100, then 9.2 per ct. of its heat value 

 passed from the ox in the undigested matter of the solid excrement. 

 This loss we may compare to bits of coal passing unburned thru 

 the grate bars of a furnace. While undergoing digestion, large 

 quantities of gas, called methane, were formed. This gas was 

 taken from the intestines by the blood and given off thru the lungs 

 and skin, a loss of 9.3 per ct. resulting. There was a further loss 

 of 3.9 per ct. in the urea which left the body in the urine by way 

 of the kidneys. The sum of these three losses is 22.4 per ct., which 

 measures that portion of the total fuel value of the corn meal 

 which was of no value to the ox, but really worse than useless, 

 because work was required in passing it thru the alimentary tract. 

 The remaining 77.6 per ct. represents the available energy of the 

 corn. 



73. Losses due to mastication, digestion, and assimilation. From 

 this 77.6 per ct. of available energy must be deducted the energy 

 expended in the work of mastication, digestion, and assimilation, 

 amounting to 36.3 per ct. of the total fuel value of the corn. Sub- 

 tracting this last sum and the previous losses from 100, there re- 

 mains 41.3 per ct. as the net energy value of the corn, or the amount 

 which the animal may use for repairing body tissue, for growth, 

 for the laying on of fat, or for the production of external work. In 

 the case of timothy hay only 14.7 per ct., and with wheat straw 

 but 6 per ct., of its original fuel value remains as finally available 

 for such purposes. About one-half of the total fuel value of these 

 two feeds passed off as undigested matter, this portion never having 

 been inside the body proper. 



In noting the heavy losses shown under the column headed "Pro- 

 duction processes," the following points are of interest: Zuntz 

 found that the work of the horse in chewing hay and preparing it 

 for swallowing required 4.5 per ct. of the total energy in the hay, 



