-218 



when thawed to recover vital action, is a fact, says 

 Mr Hunter, so well attested, that we are bound to 

 believe it. 



176. Amphibious animals exhibit a great variety 

 in the structure of the respiratory organs, and, con- 

 sequently, in the degrees of animal heat. Frogs and 

 land tortoises possess a temperature about five de- 

 grees higher than that of the medium they inhabit, ac- 

 cording to Dr Martine. The same may be said of 

 sea tortoises, toads, vipers, and all the serpent kind, 

 all of whom have lungs of the same fabric, and the 

 same cold constitution of body *. Mr Hunter ob- 

 served, that the frog and toad were about four or 

 five degrees warmer than the atmosphere when it 

 was at 35 or 36 : and that some hours after 

 ck'ath, they gradually fell down to the temperature 

 of the surrounding air f. This difference of tempe- 

 rature appears to increase in a warmer atmosphere : 

 for Mr Carlisle kept three frogs for many days 

 in an equable atmosphere of 54, and their sto- 

 machs preserved a temperature of 62 J. In an 

 atmosphere of 58, Mr Hunter found the ther- 

 momter, introduced into the stomach of a healthy 

 viper, to stand at 68 ; but, after the animal was put 

 into a pan, and the pan into a cold mixture of 10, 

 where it remained about ten minutes, the heat was 

 reduced to 37, and in twenty minutes more to 31, 

 nor did it sink lower : its tail now began to freeze, 



* Essay on Thermometers, p. 142. 

 f Treatise on the Blood, p. 298. 

 Philosophical Transactions, 180. 



