482 
ON THE MEDICAL TOPOGRAPHY OF SINGAPORE. 
while the town itself is, as stated by Dr. McCulloch ** a land where 
fevers are unknown.” The deductions I would make from that are, 
1st. temperature in this instance cannot be a cause of fever, as the 
difference of temperature about 1° lower, is in favor of the fever ge¬ 
nerating district. 2d. The state of moisture—fall of rain, electricity, 
winds, and currents of air, all these can have no effect in making the 
one place more healthy than the other, as from the proximity, the 
same meteorological changes must be felt in botli places at the same 
time, indeed the palm of superiority in all these respects would be 
carried off by the fever generating locality, which has free ventilation, 
and an atmosphere not polluted by the respiration of thousands of 
human beings, nor the effluvia from the filth of as many thousands of 
natives, who know not the charms of cleanliness. There is only one 
inference to be made, and that is, that although both the town and 
the country are possessed of swamps, those near town are under tidal 
influence and those in the country not, and that as we find the town to 
be exempt from fever, and the country not, we must attribute to the 
swamps in the country the fever, and to the state of these swamps, 
viz., their freshness and their not being subject to tidal influence, 
the generation of malaria, as in these respects only, do they differ 
from the swamps in town. 
Having X think clearly shewn that a locality contiguous to fresh 
water swamps is obnoxious to fever, and that it is not so when con¬ 
tiguous to swamps subject to tidal influence, the conclusion to be 
drawn is that either some malarious influence is generated in fresh 
water swamps which is not in those subject to tidal influence , or, 
if generated, that there is some counteracting agent which ren - 
ders the malaria innocuous. 
In a former part of this Paper I have stated the gaseous products 
of decomposing vegetable matter to be carbonic acid and earburetted 
hydrogen, and where sulphurets are present sulphuretted hydrogen. 
Where animal matter exists with vegetable there is in addition am¬ 
monia. These are the known and acknowledged gaseous products 
of marshes and are by some considered as the Malaria. 4 4 Car¬ 
bonic acid and sulphuretted hydrogen which are frequently evol- 
