J 48 Dr. Edwards, De V Influence 



vent their putting their heads above the water, so that th& 

 assertion is but a negative kind of proof that they remain sa 

 long under the water without coming up to respire, as some 

 affirm. M. Bose declares he watched frogs approach the 

 surface at regular periods every day during the winter sea- 

 son. Under the most favourable circumstances Dr. Edwards 

 found that frogs could not remain submersed, in winter, more 

 than two days and a half. Frogs are less active during 

 winter than at the other seasons, but they never lose their 

 motion. Were it true, as Spallanzani thinks it is, that thejr 

 remained so long under water, it is probable that they would 

 become frozen in winter and die. Spallanzani derives his 

 opinion from what occurs with fish, forgetting that frogs are 

 amphibious, and live as well on land as in water ; whereas 

 fish are limited to a watery medium, and can, therefore, fur- 

 nish no example. 



Dr. Edwards found that frogs, placed in certain quantities 

 of aerated and non-aerated water of an equal temperature, 

 lived longest in the former ; but that the difference was not 

 constant in its results, being often twice as long in one case 

 as in the other, as to the duration of life. 



The next inquiry regarded stagnant water renewed at in- 

 tervals, and in this the duration of life was prolonged beyond 

 the term of the last experiments, and even to eight days» 

 During winter when the temperature was lowest the frogs 

 remained active, though less so than in spring. 



The conclusions to be drawn from these experiments are, that 

 frogs pass the winter in an animated state in water, not be- 

 coming stiffened as in ice, and that they need not to approach 

 the surface of the water in order to respire, provided the 

 water they inhabit be renewed at intervals; but if the water 

 be not renewed, or if disaerated water be employed, the frogs 

 perish. 



Considering that these animals are truly amphibious, these 

 results are very curious ; and it is interesting in a physio- 

 logical point of view, to know that frogs are able to respire 

 the air contained in the dense medium of water for an inde- 

 finite period, and just as easily as they breathe the finer 

 medium on land. 



Respecting the action of aerated water on the skin, the 

 conclusion drawn seems to be correct, that it must be from 

 cutaneous absorption that the air contained in the water 

 promoted the continuance of life in Dr. Edwards's experi- 

 ments upon this point, since the animals were in a state of 

 asphyxy regarding respiration by the lungs; and that na 



