94 
POPULAR SCIENCE REVIEW. 
The paramount necessity which exists, according to these 
instances, for fresh ah’, equally holds good iu less extreme 
cases. Just as surely as a total deprivation of oxygen, or the 
presence with it of any excess of deleterious gases, produces 
death ; so the breathing of a partially-inhaled atmosphere is 
equally certain to occasion sickness and disease, if its inhalation 
be persisted in. The evils of exhausted ah’ are also more to be 
guarded against, because persons can live in it without being 
aware of its danger, as far as their sensations are concerned. 
When we enter a crowded assembly on a cold day, the air is 
always at first repulsive and oppressive ; but these sensations 
gradually disappear, and we then breathe freely, and are un- 
conscious of the quality of the atmosphere. Science, however, 
reveals the fact, that the system sinks in action to meet the 
conditions of the impure air ; but it does so at the expense of a 
gradual depression of the vital functions ; and when this is con- 
tinued, disease follows. No disease can be thoroughly cured 
when there is a want of ventilation. It is related, that illness 
continued in a family until a pane of glass was accidentally 
broken, and then it ceased : the window not being repaired, a 
plentiful supply of fresh air was admitted. Nearly all the 
churches in the empire require some artificial means of ventila- 
tion to render them physically fit receptacles for the body 
during a prolonged service. The Sunday-schools also, as a 
general rule, are very ill ventilated ; and lessons in the second 
hour are far worse rendered than in the first, solely arising 
from a semi-lethargic coma that comes over the pupils breathing 
a carbonic air, which has already done duty and been inhaled 
by others several times. However much to be regretted, it is 
still Hue that people •will sometimes sleep during the sermon. 
Now, the minister must not be twitted with this ; for with the 
oratory of a Jeremy Taylor, or of a Tillotson, people could not 
be kept awake in an atmosphere charged with carbonic acid, the 
emanations of a thousand listeners.* 
Instances innumerable might be pointed out in connection with 
our trades and professions, showing that no one can break with 
impunity the law of nature, which demands that the food 
destined to nourish and warm the body should be convei’ted 
into heat, and vitalised by a constant supply of fresh and pure 
air. The importance of this subject becomes more evident if 
we turn to a few statistics. In a life of fifty years a man makes 
upwards of 500 millions of respirations, drawing through his 
lungs nearly 170 tons weight of air, and discharging nearly 20 
tons weight of the poisonous carbonic acid. It has been also 
calculated that, to ventilate a room effectually, every person 
* Pi esse. 
