29 



vie," says Cuvier, " est done un tourbillon, plus 

 ou moins rapide plus ou moins complique,"- 

 but nothing similar is met with in minerals. 

 These increase merely by the accidental addition 

 of new particles to the original mass ; they dis- 

 play no motion of fluids along solids no mole- 

 cular interchanges of the two nor have they any 

 action with the external world, except such as is 

 strictly either chemical or mechanical. 



In the second place, organic substances are 

 capable, so long as the changes just alluded to 

 are going on, of resisting and modifying the action 

 of heat and cold, of moisture, and of chemical 

 agents in general, to a most remarkable degree ; 

 arid this property of self-preservation is in them 

 so striking, as to have been regarded, from a very 

 early period, to be the most essential attribute of 

 life. It is well known that plants in general 

 are commonly above the temperature of the sur- 

 rounding medium, if that be low, and inferior to 

 it, if it be high nay, that some of them vegetate 

 in perfection in water, the temperature of which 

 is sufficient to have boiled them, had they been 

 deprived of life, and this property of resisting 

 cold and heat is still more remarkable in animals. 

 The living egg is generally above the temperature 

 of the atmosphere, and it is frozen with great 

 difficulty ; arid the power possessed by the higher 

 classes of animals, and particularly by man, of 

 preserving a more or less uniform temperature, 

 under extremes of cold and heat, is almost un- 

 limited. In very cold climates, the thermometer 



