30 
PR. W. MARCET ON A CHEMICAL INQUIRY INTO 
for the experiments taken collectively amounted to 0'0942 litre for a fall of 10 mm. ; 
and with another it amounted to 0‘179 litre. It follows that the effect of falling 
atmospheric pressures varies in degree with different individuals. The curve shows 
distinctly, in the case of C. F. Townsend, the same influence of a falling barometer 
on respiration as the curve for W. Alderwood. From 0 to 2 hours after food, 
and from 4 to 6 hours after food, there is a distinct fall; from 2 to 4 hours after food 
the fall is still observed though less marked, showing again that food appears to 
lessen the influence of the atmospheric pressure on respiration. 
The results obtained from the present inquiry are as follows :—- 
1 . The phenomenon is confirmed that less air, reduced to 0 ° C. and 760 mm., is 
breathed at high than low altitudes, for the formation in the body of a given weight 
of carbonic acid. 
[2. The experiments on W. Alderwood certainly show that a local fall of tempera¬ 
ture is attended with a sliMit I'eduction in the volumes of air breathed for the for- 
O 
mation and expiration of 1 grin. COg, a phenomenon similar to that resulting from a 
fall of atmospheric pressure.—25th February, 1890.] 
3. The influence of food, during digestion, on the formation of carbonic acid, com¬ 
mences within the first hour after a meal ha,s been taken, and lasts for two or three 
hours, the period for the maximum amount varying throughout that time. 
4. The influence of food on the relation between the volumes of air breathed and 
the corresponding weights of caiTonic acid ex])ired is clearly shown, the volumes 
following, more or less, the fluctuations in the carbonic acid ; but tlie CO 3 expired has 
a marked tendency to fall more rapidly than the corresponding volumes of air as time 
elapses after a meal. The harmony of the tracings appears to recover itself, however, 
over niglit, and the lines are again nearly parallel before the first morning meal. 
5. Tlie variations of local atmospheric pressures have a marked influence on respira¬ 
tion, less air being taken into the lungs for the formation and emission of a given 
weight of carbonic acid under lower atmospheric pressures than under hnjher pressures ; 
but this influence varies in degree according to dilierent persons. In the present 
inquiry with two subjects ex])erimented upon ; in one case, for a fall of pressure 
of 10 mm. (0’394 inch), there was a mean reduction of 0’094 litre in the volume of 
air breathed for 1 grin. COo expired ; in the other case, the reduction was greater, and 
amounted to 0’179 litre. 
6 . Tlie influence of atmospheric jiressures on the volume of air breathed is 
apjiarently not the same throughout the whole day, being somewhat less maiked 
from 2 to 4 hours after a meal, when the action of food may be considered ai its 
maximum. Thus, digestion apparently reduces more or less, the eflects of any local 
change of pressure on respiration. 
The present investigation shows beyond doubt that different individuals breathe 
different volumes of air to burn in the body and expire a given weight of carbonic 
acid. The two ])ersons experimented ujion on the present occasion yielded respec- 
