1878.] 
to Health and Comfort. 
205 
of the simple rules applicable to the gaseous and metallic 
elements, it was thought that the cause of disease or health 
was to be discovered. Careful observers then examined, 
from the chemical standpoint, the constitution of the air, 
both fresh and vitiated ; and writers, with good logical con- 
clusions, enunciated a theory , b}' which it was made evident 
that chemistry had uncovered the root of disease, and car- 
bonic acid gas was the fatal cause. 
The real fads are these : — An adult in still life inhales 
each minute about 480 cubic inches of fresh air, and exhales 
488 cubic inches of vitiated air, of which vitiated air about 
4 per cent is carbonic acid, and from which about 19 per 
cent of the oxygen originally supplied by the fresh air has 
been abstraded ; the original quantity of vapour in the 
fresh air at mean temperature and hygrometric condition 
(62° and 65 per cent) will have been increased from ri to 
3* 08 grains. 
Carbonic acid gas was made the scapegoat. It killed 
dogs at the Grotto del Cane, as was happily exhibited to 
numerous travellers in Italy at that time — and both before 
and since, the same unfortunate dog serving to be killed, to 
the satisfadion of admirers, that had been resuscitated the 
day before, after the visitors’ backs were turned. It was 
heavier than air, and in some conditions of temperature 
would not so readily diffuse, but form a layer of distind gas, 
like water beneath oil. Altogether it answered the condi- 
tions of hypotheses, and it was decided to be vile, delete- 
rious, poisonous. To be sure we devoured it in bread, and 
drank it in beer or aerated waters, but then the poison was 
to the lungs, not to the stomach ! This theory found pro- 
mulgators in the ledure-rooms and advocates in the house- 
hold thirty years ago, and has become to-day the traditional 
belief of the middle-aged and elderly. If a room is hot or 
close from excess of temperature, or from a crowd of occu- 
pants, carbonic acid gas is the difficulty ; if malaria is deve- 
loped in a jail or hospital, or typhus or scarlet fever exist in 
the dwelling, carbonic acid gas in excess is the poison. 
“ The gas is heavier than air, and must necessarily sink to 
the floor, where all the air of vitiation will be found.” 
These notions continue to have advocates and supporters to 
the present time, and the popular ledurer or writer gives a 
half assent to them to secure the favourable opinion of 
audiences or readers. But step by step, during the past 
thirty years, it has come to be perceived that the causes of 
disease are not to be found with organic matter, and car- 
bonic acid has been removed from its elevated place in 
