
° CONSERVATION OF ENERGY IN LIVING ORGANISM. II9 
in experience and in the number of experiments the total aver- 
ages of income and outgo approach each other more nearly and 
that the grand totals may be regarded as identical. 
Of course such discrepancies as have been pointed out are 
far within the limits of experimental error and physiological 
uncertainty. As we said in a similar summary in a previous 
publication,* the agreement of average results is much closer 
than was originally hoped for, and it is by no means certain 
that future averages will show so exact a balance. ‘The elec- 
trical and alcohol check tests described earlier, (page 112) 
show that the measurements of energy by the apparatus, 
though subject to minor errors in short periods, become nearly 
exact when several tests are averaged. 
It seems certain that the respiration calorimeter itself is an 
apparatus of precision. The results reached by its aid are 
fully as accurate and reliable as those ordinarily obtained in 
the use of what are considered well developed forms of appara- 
tus and methods in the chemical laboratory. ‘To be sure, they 
are not equal in refinement to those used in the most accurate 
determinations of atomic weights, and they do not compare 
with the best physical measurements; nor are they yet by any 
means perfected as agencies for the special forms of research 
for which they were intended. The errors found in the results 
of individual tests are much larger and more numerous than is 
to be desired and attempts toward improvement are constantly 
made. Indeed much more labor has been given to the de- 
velopment and testing of apparatus and methods during the 
past eleven years than to actual experiments with men, and 
“tquch more will have to be done in coming years to the same 
end. ‘The direct determination of the amount of oxygen used 
in metabolism is one of the problenis which surely needs solv- 
ing and on this we are now working. But so far as the meas- 
urements of the energy given off from the body in the form ~ 
of heat and the heat equivalent of muscular work are concerned 
the apparatus serves its pupose very well. 
The same may be said of the bomb calorimeter as developed 
and used in this laboratory for the measurement of the poten- 
tial energy of food and unoxidized excreta. This means that 
the net outgo of energy is measured with reasonable accuracy, 
especially when the results for long periods are available. 

* Connecticut (Storrs) Station, Rpt., 1900, p. 129. 
