75 2 
CHEMISTR Y OF RESPIRATION. 
There is an irregular increase of the vital capacity with weight, and as 
regards age there is an increase from 15 to 35 years, and then a decrease 
from 35 to 65 years, even when height is 
taken into consideration. When a man is 
standing, his vital capacity is 260 cub. in. ; 
in sitting erect, recumbent, and prone posi- 
tions, it is 255, 230, and 220 cub. in. 
respectively. 
On the opposite page the average 
amounts of complemental, tidal, reserve, 
and residual air are given, but it is 
necessary to point out again that they are 
only approximate values. The several 
volumes have already been shown to vary 
considerably in different individuals. 
Hermann 1 subdivides the residual air 
into collapse air, the quantity driven out of 
the lungs when the thorax is opened ; and 
the minimal air, the quantity which re- 
mains in the collapsed lungs. 
In newly-born children the volume of 
each inspiration in quiet breathing is 35 c.c, 
but during screaming it is raised to 61 c.c; 
the vital capacity is about 120 c.c. The 
volume of the lungs of four children born 
dead at full term was 40, 55, 55, and 60 c.c. 
respectively, and when blown out they con- 
tained 25, 30, 50, and 90 c.c. of air respect- 
ively.' 2 For the first few days of life the 
lungs completely fill the opened thorax ; 
there is no collapse air ; the residual air is 
the minimal air. The lungs during each 
expiration become almost free from air, and 
the ventilation is very great, the renewal 
of air being almost perfect.-' 5 
For the determination of the volumes 
of air present in the lungs under different 
conditions, Hutchinson used a special 
meter, which he termed a spirometer. The 
construction of this apparatus is shown in 
Fig. 68. 4 
Since that time many simpler and 
improved forms of spirometer have been 
introduced. 5 The most important precau- 
tion is to reduce the resistance of the meter 
as much as possible, otherwise the depth 
and frequency of respiration become ab- 
normal. 
1 "Lehrbuch der Physiol.," Berlin, 1896, Ann. 11, S. 126. 
3 Eckerlein, Ztschr. f. Geburtsh. u. Gynak., Stuttgart, 1890, Bd. xix. S. 120. 
3 Hermann, loc. cit., S. 127. 
4 For further details, see Hutchinson, article "Thorax," Todd's " Cyclopaedia of 
Anatomy and Physiology," vol. iv. p. 1069. 
5 Fleischl von Marxow, Ccntralbl. f. Physiol., Leipzig u. Wien, 18S8, S. 39; Clar, 
Wien. klin. Wchnsclir., 1889, No. 18 ; Marcet, " Proc. Physiol. Soc." Journ. Physiol., Cam- 
bridge and London, 1897, vol. xxi. ; Hanriot and Richet, Compt. rend. Soc. de biol., Paris, 
1887, p. 405. 
Fro. 68. — Hutchinson's spirometer. 
