LECT. XL ACTION OF CALORIC. 219 



-1-32 [ = 89-6 Fahr.] from thirty to twelve minutes ; 

 and at + 42 centig. [ = 107-6 Fahr.] death was instanta- 

 neous. 



The very great influence exercised by slight variations of 

 temperature upon the life of frogs, cannot be ascribed to 

 the different quantity of air dissolved by the water at these 

 different temperatures. We know, indeed, that this varies 

 very little in different seasons, and yet we have seen that 

 the differences of temperature of the year produce very 

 marked effects upon the life of frogs immersed in water. 



Edwards found that the quantity of air which these ani- 

 mals respire is greater in proportion to the higher tempera- 

 ture of the medium in which they live ; so that the quantity 

 \vhich is usually dissolved in water, even when constantly 

 renewed, is not sufficient for them if the temperatnre be at 

 all elevated. Frogs, then, only live in water at very low 

 temperatures ; except they can come to the surface, and 

 respire atmospheric air. We observe, with fish, analogous 

 phenomena. Immersed in a certain quantity of water con- 

 taining air in solution, but which rs not in contact with the 

 atmosphere, the duration of their life is longer in proportion 

 as the temperature of the water is lower. 



We have already described an experiment of this kind, 

 made on a torpedo contained in water at -f 28 centig. 

 [ = 82-4 Fahr.;] it soon died, in giving a series of strong 

 shocks; and, on the contrary, lived a long time in cold 

 water, giving few and feeble discharges. 



The relation found between the respiration and the tem- 

 perature of the medium, in which the animals, we are now 

 speaking of, live, is a further proof of the chemical nature 

 of this function. 



Man, and mammals in general, are able to support a 

 temperature much higher than that which is proper to them. 

 The observation of Tillet and Duhamel is well known. 



