TORPIDITY. 75 



50, these animals become torpid, and suffer their tempera- 

 ture to sink as low as the freezing point. When reduced 

 below this, either by natural or artificial means, the vital 

 principle is in danger of being extinguished. In this torpid 

 state, they respire very slowly, as the circulation of the, 

 blood can be carried on independent of the action of the 

 lungs. Even in a tortoise kept awake during the winter 

 by a genial temperature, the frequency of respiration was 

 observed to be diminished. 



The circulation of the blood is diminished, in proportion 

 to the degree of cold to which these torpid reptiles are ex- 

 posed. SPALLANZANI counted from eleven to twelve pulsa- 

 tions in a minute in the heart of a snake, at the tempera- 

 ture of 48, whose pulse in general, in warm weather, gives 

 about thirty beats in the same period. Dr REEVES made 

 some very interesting experiments on the circulation of the 

 toad and frog. " I observed," he says, " that the num- 

 ber of pulsations in toads and frogs was thirty in a minute, 

 whilst they were left to themselves in the atmosphere, of 

 which the temperature was 53 ; when placed in a medium, 

 cooled to 40, the number of pulsations was reduced to 

 twelve, within the same period of time ; and when expo- 

 sed to a freezing mixture at 26, the action of the heart 

 ceased altogether *." 



The powers of digestion are equally feeble during torpi- 

 dity as those of respiration or circulation. Mr JOHN HUN- 

 TER conveyed pieces of worms and meat down the throats of 

 lizards, when they were going to their winter quarters, and, 

 keeping them afterwards in a cool place, on opening them 

 at different periods, he always found the substances, he had 

 introduced, entire, and without any alteration ; sometimes 

 they were in the stomach, at other times they had passed 



* Essay on Torpidity, p. 19. 



