J46 Pr. Edwards, De Vlnflumoe 



continuance of life, generally, in these experiments, varied 

 from one to two hours and twenty-seven minutes. The mean 

 term of life was pne hour and thirty -seven minutes, as ave- 

 raged in July, and in September one hour and forty-five 

 minutes, the two extremes of the seasons approximating the 

 effects. The duration of the frog's existence was greatest in 

 the greatest depression of temperature. Thus at ten degrees 

 the duration of life was more than double what occurred at 

 sixteen or seventeen degrees, and at zero it was about triple. 

 As the heat was increased, the duration of life was dimi- 

 jiished ; at forty-two the frogs died, and in the lowest tem- 

 perature they lived longest. 



It appeared that at zero the frogs did not become stiffened, 

 but retained their motion, and their resistance to the frozen 

 state is the cause of the continuance of their existence at a 

 low temperature. The cause of this resistance is to be found 

 in their peculiarity of constitution. Toads produced similar 

 results. 



It may be alleged that frogs naturally live in climates at 

 from forty to forty-two ; but, it is to be observed, that they 

 are then placed in a situation of liberty to come to the sur- 

 face of the water to respire when they please ; whereas in 

 these experiments their respii'ation is limited, fropa their ina- 

 bility to reach the surface. 



Taking a wider range of temperature, Dr. Edwards sought 

 to ascertain the influence of the seasons. In July and Sep- 

 tember frogs were found to live from one to two hours and 

 twenty-seven minutes in aerated water at fifteen and seventeen 

 degrees. In November they died at the end of more than 

 double this period, under the same temperature, and all other 

 circumstances being similar excepting the season. As the 

 autumn advanced life was prolonged. 



To what are we to ascribe the modifications of the seasons ? 

 Probably to circumstances appertaining to the intensity of 

 light, to electricity, to temperature, to the pressure of the 

 atmosphere, to dryness and moisture, &c. ? Such existing 

 causes naturally suggest themselves. But it appears that little 

 or no account can be rendered as to pressure, since its varia- 

 tions were too trifling during the two seasons. Moisture 

 could not effect an influence, because the experiments were 

 performed in water. The motion of the air was also obvi- 

 ated. Of all the suggested modifications temperature alone 

 acted, and this, as it related to the surrounding air, was ren- 

 dered ineffectual by artificial temperature. The animals, 

 therefore, could only be affected as to the temperature of the 



