THE FOOD AS A SOURCE OF ENERGY. 289 
Food, F 7 Urine Methane, Metaboliz- 
Cals. Cals.” | (Corrected), | Cais’ | able Energy, 
Period 7........ 46,275.0 | 14,104.8 | ~ 2,593.0 3,564.2 | 26,013.0 
see. Ceara 30,338 .1 8,574.9 1,795.0 2,579.4 | 17,388.8 
Difference....| 15,936.9 5,529.9 798.0 984.8 8,624.2. 
Correction ....| —208.3 —58.9 —12.3 -17.7 —119.4 
15,728 .6 5,471.0 785.7 967.1 8,504.8 
Percentagés. . . 100.0 34.78 5.00 6.15 54.07 
In these computations it is assumed that the increased metabo- 
lizable energy of the ration is derived entirely from the added feed- 
ing-stuff, or, in other words, that the latter exerted no influence 
either upon the digestibility of the basal ration or upon the propor- 
tion of its energy lost in urine and in hydrocarbons. That such is 
the case we have no means of proving, and it is, indeed, unlikely 
that it is exactly true. The metabolizable energy of the added 
feeding-stuff as above computed includes any such effects—that is, it 
represents the net result to the organism of the added coarse fodder. 
Table I of the Appendix contains the results of all the experi- 
ments of this sort, computed in the manner illustrated above. It 
will be noted that in all but two cases the correction is less than 
in the above example. In each case the table shows also the per- 
centage of the gross energy of the feeding-stuff which was found to 
be metabolizable and the percentage carried off in each of the 
excreta, 
Summary.—The results of the foregoing determinations of the 
metabolizable energy of the organic matter of coarse fodders are 
summarized in the table on page 290, which shows the gross and 
metabolizable energy per gram of organic matter and also the 
percentage of gross energy found to be metabolizable. 
Concentrated Feeding-stuffs.—The metabolizable energy of 
the organic matter of a concentrated feeding-stuff when added to 
a basal ration can, of course, be computed by the same method as in 
the case of added coarse fodders, but, as we shall see, some special 
difficulties arise in its application. 
The only commercial concentrated feeding-stuff upon which 
such experiments have been reported is beet molasses, although 
