134 WONDERS OF ORGANIC LIFE. 



asked, are these frogs not drowned, seeing that 

 respiration is rendered impossible ? The reason 

 is evident. In the first place the action of the 

 heart is all but, or indeed altogether, sus- 

 pended, so that the merest trifle of oxygen, if 

 any at all, is required for the purposes of the 

 system. In the next place, the large cellular 

 lungs most probably contain a sufficient quan- 

 tity of air for the needful supply ; and 

 thirdly, these animals respire by means of the 

 skin as well as by the lungs ; not, however, 

 that this process takes place during their 

 hybernation. 



Wherein the hybernation of reptiles essen- 

 tially differs from the hybernation of quadru- 

 peds, except in its extreme degree of torpidity, 

 and the more complete suspension of all the 

 vital functions, we cannot tell. As they are 

 not frozen to death, but revive, surely their 

 torpidity is preservative. It is true that cold- 

 blooded animals are always inert, and some 

 torpid, when the temperature of the air is even 

 moderately low, and that they require warmth. 

 But, if not in so marked a degree, yet warm- 

 blooded animals, according to the latitude for 

 which they are respectively destined, become 

 inert under a certain degree of cold, and require 

 a certain temperature for the fulfilment of the 

 duties of active life. Eeptiles, like marmots, 

 retire to their hybernacula ; instinct directs 

 them to prepare against the advancing winter; 

 they become torpid, and thus revive. Mere 

 cold, however, will not make a dormouse torpid, 



