ON THE MEDICAL TOPOGRAPHY OF SINGAPORE. 
485 
Acid is very injurious to vegetables,” appearing “ to exhaust the vita¬ 
lity ofplants, and to cause in them a state analogous to narcotic poi¬ 
soning in animals.”—(Chrj&tlson.) M. Halle says, the symptoms, in 
cases where the vapours are breathed in a state of concentration are 
sudden weakness and all the signs of ordinary asphyxia. When the 
noxious emanations are less concentrated, several affections have 
been noticed, which may be reduced to 2 varieties, the one consist¬ 
ing of pure coma, the other of coma and tetanic convulsions.” In 
none of the “ French investigations on this singular subject has any 
allusion been made to the question, whether the health sustains any 
injury from long continued exposure to the Gas in very minute pro¬ 
portion. It is probably injurious however. At one time while in the 
practice of not using any precautions against inhaling the Gas in 
chemical reseaches, I used to remark that daily exposure to it in a 
minute quantity caused in a few weeks an extraordinary lassitude, 
langour of the pulse, and defective appetite. Mr. Taylor says, that 
the workmen in the Thames Tunnel became affected with giddiness, 
sickness, general debility and emaciation, then with a low fever at¬ 
tended with delirium, and in the course of a few months several died. 
No cause could be discovered except the frequent escape of Sulphur¬ 
etted Hydrogen from the roof.”—(Christison.) 
From these extracts we see that this Gas does possess very inju¬ 
rious effects when breathed in a concentrated form, we and cannot but 
suppose, that even in a much diluted form it must he injurious. In¬ 
deed to such an extent was it supposed to be so that the fever which 
attacked those who navigated the Niger was attributed by Professor 
Daniell to the existence of this Gas in the water of the river, and the 
specimens of the water when brought to England freely evolved the 
gas ; but the Editor of the Brit: and For: Med : Rev: No. xxxi p. 
263, says, “ the section on the causes of fever is valuable, but throws 
no new light on the subject except to disperse the theory promul¬ 
gated some time before the sailing of the expedition from England, 
that the existence of free Sulpheretted Hydrogen Gas in the waters 
of the Niger might account for the fever. Dr. McWilliam shews in 
the most satisfactory manner that no such gas is found in the Niger, 
