on which the action of the heart depends, &c. ^5 
much less increase of the heart’s action than arose from the 
spirit of wine. The increased action was greater from the 
opium, than from the tobacco. The first effect of both was 
soon succeeded by a more languid action of the heart than 
that which preceded their application to the brain. This effect 
was greatest, and came on soonest when the tobacco was used, 
and we always, for we frequently repeated the experiment, 
saw an evident increase in the action of the heart, when we 
washed off the tobacco. We could also perceive this, though in 
a less degree, when the opium was washed off. Little or none 
of this debilitating effect was observed when the spirit of wine 
was used. After its stimulating effect had subsided, the ac- 
tion of the heart only returned to about the same degree as 
before the application of the stimulus. 
Exp. 15. The foregoing experiment was repeated on an 
animal of cold blood. Mr. Hastings had found, that im- 
mersing the hind legs of a frog in tincture of opium, in less 
than a minute, deprives it of sensibility. This does not arise 
from any action of the opium ; a watery solution of opium, we 
found, however strong, does not produce the effect. It is 
immediately produced by simple spirit of wine, and arises 
from the action of the spirit on the nerves of the part to which 
it is applied, for it takes place quite as readily as in the healthy 
frog, after a ligature has been thrown round all the vessels 
attached to the heart. It is remarkable, that if simple spirit 
of wine is used, the animal expresses severe pain, if tincture of 
opium, very little. I have already mentioned the reason why it is 
necessary, in order to judge of the result of this experiment, 
that the animal should be rendered insensible. (Exp. 11.) 
Having thus deprived a frog of sensibility, we laid bare the 
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