
236 STORRS AGRICULTURAL EXPERIMENT STATION. 
This difference in experiment No. 6 amounts to 3.2 per cent 
and in experiment No. 9 to 1.1 per cent. of the energy of the 
material oxidized. ‘T‘his discrepancy may be due to errors of 
experiment, of which several are possible. One may be found 
in the sampling of the food materials. Our experience has | 
shown that the error from this source may be much larger than | 
is commonly supposed. Special measures for avoiding it were 
adopted in later experiments, in which the discrepancies were 
considerably less, as in No. 9. Another important source of 
error may perhaps be sought in the composition of the materials 
gained or lost in the body, and in their assumed heats of oxi- 
dation. A very similar source of error, and one perhaps the 
most dificult to eliminate, is the variation in the amount of 
material actually absorbed from the alimentary tract. It is not 
unreasonable to assume, however, that after a four days’ pre- 
liminary experiment in which a constant diet is used the rate 
of assimilation is fairly constant, and that the material actually 
absorbed on the ‘last day will not vary materially from that ab- 
sorbed on the first day of the respiration experiment proper. 
Of the other sources of error there was one of ‘special con- 
sequence in this experiment. The muscular work of the sub- 
ject was at times rather severe, and the heat was developed 
within the apparatus at a rapid rate, and the changes in tem- 
perature inside the chamber were considerable. We are 
inclined to think that the heat measurements under these 
circumstances were less accurate than usual, and that minor 
modifications of the apparatus may be needed to provide for 
greater accuracy in experiments of this class. 
The experience in handling the apparatus and in sampling 
and analyzing the food has been used in a number of experi- 
ments since No. 6, of which No. 9 is one. In these later 
experiments, the details of which are soon to be published, the 
differences between income and outgo of energy range from 2.2 
fo 0.4 per cent. and average about 1.2 per cent. [hat "eae 
say, in these more accurate experiments about 99 per cent. of 
the potential energy of the material metabolized and oxidized 
in the body is accounted for in the kinetic energy given off in 
the forms of heat and external muscular work. 
In how far this fairly close agreement is due to a counter- 
balancing of errors it is impossible now to say. But in view 











