VENTILATION. 
633 
They go on to say—“The practical argument as to the 
amount of fresh air required to ventilate a room is, in our 
opinion, of far more weight than the mere scientific one. 
We find, for example, that nature has provided in the atmo¬ 
sphere unlimited extent, and constant means of purification 
and of movement.’ 5 
The building of dwellings interferes with those natural 
conditions, by enclosing the air in confined spaces, saturating 
that air with impurities, and rendering it stagnant. It may 
be fairly argued, as, indeed, has been proved by experience, 
that those dwellings are the most healthy in which the 
natural conditions of the atmosphere are most perfectly 
preserved. 55 
Chemistry has told us distinctly enough that at least 200 
cubic feet of air per hour is required by a human being for 
the mere purposes of diluting the carbonic acid and water 
given off from the body to the same standard as they exist 
in the atmosphere itself. 
But chemistry takes no cognisance of those aerial poisons 
eliminated from the skin and lungs, and which in stagnant 
air are perfectly cognisable to the senses, even after the air 
has been diluted to the extent stated. 
Indeed, the object to be served by ventilation is primarily the 
dilution and removal of these poisonous exhalations; and if this 
be secured , the carbonic acid and water will be removed at the 
same time.* 
It has been estimated by Doctor Arnott that each adult 
individual vitiates per minute by respiration 400 cubic inches 
of air, and by pulmonary and cutaneous transpiration three 
cubit feet. 
A horse would therefore vitiate by respiration 2000 cubic 
inches, and by pulmonary and cutaneous transpirations fifteen 
cubic feet in the same space of time. 
Fires, lamps, and candles, are calculated by Tredgold to 
deteriorate air at the rate of one fourth a cubic foot per minute 
for each individual; and, although the horse is not usually 
subject to this deterioration, yet the absence of a fire-place, 
the retention of faecal and urinary matter in the stable, and 
the fact of his having to breathe again air which, owing to 
the ordinarily confined space in which he is placed is charged 
with carbonic acid, all add to the impurity of an atmosphere 
already vitiated; for the insalubrity of the air is in the 
ratio of the carbonic acid diffused through it. If this exceed 
a half per cent., the atmosphere, according to Leblanc and 
* See * General Report of the Commission appointed for Improving 
the Sanitary Condition of Barracks and Hospitals,’ 1861. 
