82 AMPHIBIA. 
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The existence of cutaneous respiration in the Frog was 
proved by the simple experiment of tying a piece of blad- 
der over the head so tightly as to prevent the possibility 
of communication with the lungs, so as indeed to produce 
complete strangulation. The Frogs were then placed 
under water; and on examining the air contained in the 
vessel after an hour or two, a sensible quantity of carbonic 
acid was detected. 
On placing Frogs in vessels filled respectively with river 
water, and with water which had been deprived of air by 
boiling, and inverted over the apertures contained in the 
shelf of a pneumatic trough, containing about ninety-eight 
pints, those in the latter lived on the average little more 
than half as long as those in the aérated water. On trying 
the effects of submersion under stagnant water frequently 
renewed they lived two months and a half, and then died 
from accidental neglect of changing the water. The re- 
sults of placing them under running water were similar: 
in this case they were confined in a sort of cage, and sunk 
inariver. The effects of temperature in all these experi- 
ments were amongst the most curious and interesting cir- 
cumstances connected with the inquiry. These results 
prove that the duration of life under water is in an inverse 
proportion to the elevation of the temperature from 32 
degrees to about 107, at which point the animals die almost 
instantly. But these effects of temperature were found 
to be modified by an increase of respiration, whether by 
their rising to the surface and breathing the atmosphere, 
or by the quantity of aérated water being increased. 
Such is a slight glance at the results obtained with 
reference to the cutaneous respiration carried on through 
the medium of aérated water ; and those connected with 
the atmospheric respiration of the same surface are no less 
