492 
ON Tilt! MEDICAL TOPOGRAPHY OF SINGAPORE, 
nerated in marshes subjected to tidal influence, that there Is some, 
counteracting agent, which renders the malaria innocuous. It is im¬ 
possible to suppose that animal and vegetable decomposition does not 
take place in all rivers and swamps, subject to tidal influence, for 
we know to the contrary, that the vast accumulations at the mouths 
of rivers and even the formation of new land is the result of marine 
animalculse (Ehrenberg.)* In fact taking an “ a priori ” glance at 
our fresh water marshes and our salt ones, few would be inclined to 
doubt that the latter, so far from being devoid of animaleular de¬ 
composition and formations, even exceed the others, and the re¬ 
searches of that distinguished microseopist Ehrenberg, have fully es¬ 
tablished that fact. 1 am therefore inclined to make this inference 
that marshes under tidal influence equally with fresh water marshes 
generate malaria ; knowing the comparative healthiness of all swamps 
subject to tidal influence, another inference must therefore be drawn, 
that there are some counteracting agents in marshes subject to ti¬ 
dal influence which renders the malaria innocuous. 
The first of these agents is no doubt the rise and fall of the tide, 
which, by dissolving and diluting the soluble and putrefying matter, 
retards, as in the manner explained, further decomposition, and con¬ 
sequently the formation of malarious germs, hut the principal agent is 
In my opinion the formation of Sulphuretted Hydrogen. My reasons 
for making this startling inference are : 
First . That by the experiments of many distinguished men Sul¬ 
phuretted Hydrogen has been proved to be a most deleterious Gas 
to animal life, and even to vegetables. According to Thenard and 
Dupuytren, air containing only an 800th of Sulphuretted Hydrogen 
4 
will kill small birds in a few seconds. Chaussier has found that air 
containing a 250th of it will kill a horse, and even applying it to 
the skin of a rabbit, the animal breathing natural air, has caused its 
death. As formerly stated it destroys vegetable equally with animal 
life. If it destroys the animals themselves, is it carrying the analo- 
* That is, to a considerable extent. See Ehrenbcrg’s results: Sketch of 
the Physical Geography and Geology of the Malay Peninsula: ante, p. 
135,—Kn. 
