REPTILES AND BATRACHIANS. 



CHAPTER I. 



REPTILES GENERALLY. 



THERE are certain characteristics which belong alike to the whole 

 of the class Reptilia, and for the present we may include the 

 Batrachia. All are cold-blooded ; that is, they have not sufficient 

 warmth in themselves to maintain a given bodily heat under 

 adverse circumstances. In popular words, they are " obedient to 

 surrounding temperature." Human beings, by the healthy cir- 

 culation of the blood, and independent of external changes, main- 

 tain a temperature of about 98, which is called " blood heat." 

 We suffer discomfort from cold when the degree is much below 

 this ; and we suffer from a feverish condition when the blood is 

 much over-heated ; but reptiles, notwithstanding inability to 

 maintain such bodily warmth, suffer neither from excessive cold 

 nor extreme heat. In the latter case they are in greater vigour, 

 more alive, in fact ; and in the former condition they succumb 

 even to the verge of death without suffering. In winter, burying 

 themselves in the cold damp soil, their vitality is at its lowest, 

 some have been known to be actually imbedded in ice and yet 

 revive by a gradual thaw, and this for successive winters. I have 

 heard of snakes being found frozen and as brittle as a dry stick, 

 but recovering by gradual warmth. 



On the contrary, in the summer many of them endure tropical 

 heat, and lie basking under a sun, similar exposure to whose rays 

 would destroy the life of some animals. 



In hot countries the regularly recurring period of torpor is 

 aestivation, when many reptiles bury themselves in the mud, and 

 are literally baked up in a temporary tomb. In cooler countries 

 the hibernation is on the approach of cold weather. The total 



