82 AMPHIBIA. 



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 aerated 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 

 in a river. 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 aerated water being increased. 



Such is a slight glance at the results obtained with 

 reference to the cutaneous respiration carried on through 

 the medium of aerated water ; and those connected with 

 the atmospheric respiration of the same surface are no less 



