THE PHENOMENA OF HUMAN RESPIRATION. 
2.5 
Fall of barometric 
pressure. 
Fall in the volumes 
of air expired for 
1 grm. OOj. 
mm. 
Litres. 
0 to 2 hours after food 
180 
0-437' 
2 to 4 hours after food 
27H 
o-oio 
4 to 6 houi’s after food 
.33-7 
0-432 
Mean. 
26H 
0-293 
Therefore, for a mean fall of 26'3 mm. pressure, there was a mean reduction of 
0'293 litre in the air breathed to expire 1 grm. COg, amounting to a reduction of 
OH 11 litre for 10 mm. pressure. The small figure, O’OlO, for the fall of relation from 
2 to 4 hours after food, shows that the influence of food appears to interfere with the 
action of atmospheric pressure. It will now be seen that the fall in the volume 
of air breathed (for 1 grm. CO 3 ) is very nearly the same, whether the barometer 
readings (for every two hours) be taken collectively, or whether the extreme readings 
only be considered. If the barometer readings be taken collectively, a fall of volume 
of 0'0960 litre is observed for 10 mm. pressure; if the extreme barometric readings 
only be considered, the fall of volume will amount to OH 11 litre for every 10 mm. 
pressure. 
The experiments made at a comparatively low atmospheric temperature give similar 
results as to the effect of barometric pressures, they are, however, too few in number 
to allow of their being submitted to a special consideration. 
The experiments for barometer readings and corresponding volumes of air for the 
expiration of 1 grm. CO 2 for each person under experiment have been disposed under 
the form of curves. Tliese curves show that there is a general tendency to a fall 
of relations with a subsidence of barometric pressure, but from 2 to 4 hours after a 
meal the influence of food appears to overcome to a certain extent tiie effect of the 
barometer, the axis of the curve for relations being nearer to a horizontal line. 
The second series of experiments refers to C. F. Townsend, aged 23 years, and 
weighing 8 stone without clotlies ; no necessity was found to divide them on 
account of temperatures ; they amount to 56 in number as reported in detail in 
the accompanying Table (pp. 26 and 27). It will be seen that the maximum weight of 
carbonic acid (0‘439 grm.) and maximum volume of air expired (4'488 litres) occur 
from 1 to 2 hours after a meal; [but the excess of CO^ and air expired from 1 to 2 
hours after a meal over that expired from 0 to 1 and 2 to 3 liours after food, is 
so small that the period for the maximum effect is veiy difiicult to define. It 
has been stated in the abstract of this paper (‘ Proceedings,’ vol. 46) as one of the 
conclusions arrived at, that these researches confirm “ the known usual influence of food 
on the formation of carbonic acid in the body, the maximum expired occurring between 
two or three hours after a meal ...” This result must be accepted in a general way 
only, as the elfect of food upon the formation and elimination of CO, appears to vary 
MDCCCXC.—B. 
E 
