HEAT AND LIFE. 151 



The influence of cold on organized beings varies, ac- 

 cording as we regard superior animals or the inferior spe- 

 cies. In general, it may be said that it requires a very low 

 surrounding temperature to chill many animals, because the 

 vital heat they develop resists the process with energy. 

 Yet the mammals of arctic regions, in spite of their thick 

 coat of fur, can only brave the temperature of the pole 

 sometimes equal to 40 (cent.) below zero, the freezing- 

 point of mercury by living under the snow where they 

 make their lair. The Esquimaux, too, dig huts in it, where 

 they pass their wretched days. When the organism can 

 neither react nor protect itself against temperatures so low, 

 death by freezing quickly overtakes it. The body is stiff- 

 ened, and retains afterward a state of remarkable incorrupti- 

 bility. Every one knows the story of the antediluvian mam- 

 moths discovered in the polar ice, where they had been bur- 

 ied, as fresh as animals just dead. While heat destroys the 

 tissues, cold preserves them. 



Through what mechanical means does cold become mor- 

 tal ? It seems to act on the nervous system. Travelers 

 relate that in polar regions an unconquerable disposition to 

 sleep overcomes men attacked by very low temperatures. 

 On the icy shores of Terra del Fuego, Solander said to his 

 companions, " Whoever sits down falls asleep, and who- 

 ever falls asleep never wakes again." This inclination is 

 so overpowering that many of his attendants gave up to it, 

 and he himself sank down for a moment on the snow. It is 

 said that, during the winter of 1700, two thousand soldiers 

 of Charles XII. 's army perished in the sleep to which they 

 surrendered, under the influence of cold. Its action on the 

 nervous centres, however, is only secondary and consequent 

 on another phenomenon, studied by Pouchet, which reveals 

 this as the secret of death. When the temperature of the 

 interior of the body sinks to 10 or 12 below zero (cent.), 

 the cold freezes the blood more or less, thoroughly disor- 



