ON THE MEDICAL TOPOGRAPHY OF SINGAPORE. 
483 
ved from the earth in cellars, mines, wells, sewers and other places, 
are amongst the most venomous miasms” (Liebig); and the supposed 
existence of sulphuretted hydrogen is, according to Daniel, the cause 
of the Sierra Leon fever. If these gases in such small quantities as 
they exist in marshes can occasion fevei, they will, when in a more 
concentrated state, produce fever of a more malignant type, or even 
in the same state of dilution will, in other places and under other 
circumstances, produce the same effects, if any malarious principle 
is inherent in them ; for chemistry acknowledges no difference in the 
constitution and properties of these gases when prepared in nature’s 
vast laboratory, or in a chemist’s small one. To prevent the proli¬ 
xity of referring to numerous authorities on the properties of these 
gases, 1 will confine myself to Dr. ChrisLison’s work on poisons, the 
highest standard authority on the subject. 
Carbonic Acid. When a man attempts to inhale pure carbonic 
acid gas, the nostrils and throat are irritated so strongly that the 
glottis closes, and inspiration becomes impossible. Hence when a 
person is immersed in the gas nearly or perfectly pure, as in a beer 
vat or an old well, he dies at once of suffocation (fourth ed. p. 815.) 
M. Devergie has been led to the opinion that air which contains 5 
per cent of Carbonic Acid is amply enough impregnated to occa¬ 
sion death (p. 821). The incipient symptoms of poisoning by this 
gas, when it was estimated to be 2 per cent as a constituent of the at¬ 
mosphere, are given by Mr. Coathupe, he having closed every aper¬ 
ture in a room of the capacity of 80 cubic yards, kindled the stove 
and watched the results. In 4 hours he had slight giddiness, in 5£- 
hours intense giddiness the desire to vomit without the power, ex¬ 
cessive prostration, and incapability of muscular effort, a frequent 
full trembling pulse, a sense of distention of the cerebral arteries, 
agonising headache, but no sense of suffocation. Such are the symp¬ 
toms of a narcotic poison in a diluted though still dangerous quan¬ 
tity. The unfortunate prisoners in the Black Hole of Calcutta suf¬ 
fered from the narcotic effects of this gas, produced by the respira¬ 
tion of 146 persons confined in a room not 20 feet square ; but I 
cannot coincide with the Editor of the Indian Register, that this re- 
