APRIL 22, 1915] 
NATURE 
205 

HEALTHY ATMOSPHERES. 
PHYSIOLOGICAL research has proved that 
the cause of discomfort felt in close, ill- 
ventilated rooms is due to the physical, and not 
to the chemical, properties of the atmosphere. 
We exclude gross contamination by products of 
imperfectly combusted coal gas, e.g. from de- 
fective gas fires imperfectly flued. These chemical 
products irritate the nose and throat, and one of 
them—carbon monoxide—is a poison. We exclude 
too, those mines and factories wherein certain 
poisonous products of industry may pollute the 
atmosphere. We are writing of rooms crowded 
with human beings, of over-heated, windless 
rooms. The percentage of oxygen in such 
crowded rooms is never reduced by more than 
IO per cent., and at any of the mountain health 
resorts the concentration of oxygen is reduced 
considerably more owing to the attenuity of the 
air. Similarly the percentage of carbonic acid is 
never raised in crowded rooms to such a level that 
it has the least toxic effect. Within the lungs a 
constant concentration of carbonic acid of about 
5 per cent. of an atmosphere is maintained. The 
acidity of the blood regulates the action of the 
breathing mechanism, so that both it and the 
concentration of carbonic acid in the lung are kept 
constant. The only result of breathing an atmo- 
sphere containing o’5-1'o per cent. of carbonic 
acid—the most crowded room does not contain 
more—is a slight deepening of the respiration by 
which the concentration in the lung is kept at the 
normal figure. It becomes difficult to maintain 
the normal concentration in the lung when the 
concentration in the atmosphere rises above 3°0 
per cent.; the breathing of even a resting man 
then becomes over-laboured. The crew of a sub- 
merged submarine feels the need for fresh air when 
the CO, concentration rises above this level. 
Exact experiment, made by many competent 
researchers, wholly fails to confirm the assertion, 
so confidently made in all popular books of 
hygiene, that the expired air contains a subtle 
organic poison. The air of a crowded room smells 
offensive to one coming in from the fresh ar. and 
it may, and often does, infect us with the living 
germs of disease, sprayed out from the mouth, 
Or nose, of those who cough, sneeze, or speak, 
but it contains no organic chemical poison, and 
the fatigue and headache felt by the more sensi- 
tive occupants is certainly not due to such. These 
effects are produced by the physical properties 
of the atmosphere acting upon the nose and skin, 
on that enormous field of sensory nerves which 
‘supplies the surface of the body, contributes so 
greatly to our feelings of well-being, and regu- 
lates the metabolism of our bodies. The cutane- 
ous and nasal sense-organs are influenced by the 
temperature, movement, and vapour pressure of 
the air, and the physical qualities of the atmo- 
sphere, which control the loss of body heat by 
convection or evaporation. Out of doors we are 
ceaselessly stimulated by the play of wind; cloud, 
and sunshine, cold and heat, wet and dry alter- 
nate; monotony, the curse of the nervous system, 
NO. 2373, VOL. 95] 

is repelled. Cool, moving air braces us up; we 
are made active, eat more, and breathe more to 
keep up our body furnace. The daily turnover 
of the body is thus enlarged, the appetite is 
stimulated, and the food eaten is completely 
utilised and does not become dross and waste, 
the generator of bacterial decomposition in the 
bowel. The blood is refined out of a larger 
choice of foodstuffs, and the organs receive from 
it an ampler supply of the more precious and 
rarer building stones; the muscular exercise which 
we are compelled to take to keep warm, occasions 
the blood to circulate in ampler and quicker 
streams, and deepens the breathing, thus ensuring 
the proper expansion of the lung's, and the natural 
massage of the organs of the belly. 
We are built to be active, and keep ourselves 
warm by muscular action. By over-clothing our 
bodies and over-heating our rooms we weaken 
our vigour, expose ourselves to nutritive disorders, 
and debilitate the natural mechanism of defence 
against infective disease. Moreover, in these 
heated, stagnant atmospheres we expose ourselves 
to massive infection by those carriers of disease 
who have in their respiratory tract some strain 
of microbe exalted in virulence, and thus spread 
“colds” or influenza, pneumonia, or phthisis. 
Mere exposure to cold does not cause these ills. 
Arctic explorers and shipwrecked people who 
suffer the extremes of exposure do not suffer in 
consequence from such illness. Excessive cold 
may cause local death and gangrene, or kill by 
cooling the whole body below a viable tempera- 
ture, but our power to withstand cold is enor- 
mous, innate, the result of a million years of 
an evolution spent in struggling against the forces 
of nature. The inclement and dark wintry 
weather impels people to shut up windows, crowd 
into close, over-heated rooms, and thus expose 
themselves to massive infection. 
The sedentary worker in heated, windless atmo- 
spheres runs his metabolism at a low level, and if 
he over-indulges in the pleasures of the table, 
easily becomes the sufferer from digestive and 
metabolic ailments. It is not the bad weather 
that causes the ill-health prevalent in the winter, 
but the excessive precautions most of us take to 
avoid exposure to cold. Only the very old and 
feeble, in whom the lamp of life burns low, want 
such protection. The young and the able-bodied 
require the stimulus of exposure to the weather: 
the discomfort arising therefrom soon results in 
vigorous health, and ceases to be felt. The 
soldiers of our new armies taken from shop, desk, 
or factory, and exposed in trench or camp, have 
been singularly free from disease which is sup- 
posed to result from chit, in spite of the hard- 
ship of cold, wet, and mud. Adequately fed, 
clothed, and rested, the open-air life has made the 
clerk, shop, or clubman twice the men they were, 
given them a healthy hunger, steady nerves, a 
clear, ruddy complexion, and increased weight, 
and yet for days together their clothes may have 
been damp. 
The fear of cold and damp instilled in the 
