paratus. Similarly, there is theoretically at least an increase in
volume of the potash-lime by reason of the absorption of the carbon
dioxide. This was formerly taken into consideration, but the correction
is no longer applied.

RESPIRATORY LOSS.

With experiments on man, there is a constant transformation of solid
body material into gaseous products which are carried out into the
air-current and absorbed. Particularly where no food is taken, this
solid material becomes smaller in volume and consequently additional
oxygen is required to take the place of the decrease in volume of body
substance. But this so-called respiratory loss is more theoretical than
practical in importance, and in the experiments made at present the
correction is not considered necessary.

CALCULATION OF THE VOLUME OF AIR RESIDUAL IN THE CHAMBER.

The ventilating air-circuit may be said to consist of several portions
of air. The largest portion is that in the respiration chamber itself
and consists of air containing oxygen, nitrogen, carbon dioxide, and
water-vapor. This air is assumed to have the same composition up to the
moment when it begins to bubble through the sulphuric acid in the first
acid-absorber. The air in this absorber above the acid, amounting to
about 14 liters, has a different composition in that the water-vapor has
been completely removed. The same 14 liters of air may then be said to
contain carbon dioxide, nitrogen, and oxygen. This composition is
immediately disturbed the moment the air enters the potash-lime can,
when the carbon dioxide is absorbed and the volume of air in the last
sulphuric-acid absorber, in the sodium-bicarbonate can, and in the
piping back to the calorimeter may be said to consist only of nitrogen
and oxygen. The air then between the surface of the sulphuric acid in
the last porcelain absorber and the point where the ingoing air is
delivered to the calorimeter consists of air free from carbon dioxide
and free from water. Formerly this section also included the
tension-equalizer, but very recently we have in both of the calorimeters
attached the tension-equalizer directly to the respiration chamber.

In the Middletown apparatus, these portions of air of varying
composition were likewise subject to considerable variations in
temperature, in that the temperature of the laboratory often differed
materially from that of the calorimeter chamber itself, especially as
regards the apparatus in the upper