WINTER SLEEPERS 125 



In this, as in all other excellences, we can trace 

 a series of steps from the lower and more variable 

 condition in reptiles ; for the lowest mammals have still 

 no even temperature, nor do they suffer fever from a 

 rise of many degrees. 



In the development of every child and whelp the 

 heat-centres and heat-mechanism are only gradually 

 steadied and rendered independent of cold or heat ; 

 whilst in the winter sleep and spring awakening of the 

 dormouse, bat, and bear we see strength of constitu- 

 tion that endures a quick change of 30 degrees without 

 experiencing any harm. At such moments, which 

 break a long sequence of still winter days and preface 

 a still longer period of activity, these hibernators show 

 a reptilian fluctuation and toughness. 



The reserve and rare display of full mammalian 

 activity is well expressed by the voice. The calls, 

 chatter, and songs of birds rarely cease ; their notes of 

 warning, companionship, or exhilaration signal their 

 presence and arrest us. But with mammals it is 

 otherwise. The majority only roar, cry, or trumpet 

 to sound an alarm or in rare moments of combat 

 and excitement. Even the dog's bark is a domestic 

 refinement. The highest group, that of the monkeys, 

 is the only querulous and chattering one, and this 

 habit seems to go with active, arboreal, and social life. 

 But, whether silent or vocal, all mammals possess a 

 larynx similar to our own, and it is the nervous control 

 and adjustment of the vocal cords, of the mouth 

 and of voice-production, that give pre-eminence in 



