METABOLISM 69 



We can easily put out the candle and 

 light it again. Can we also stop life 

 processes and then cause them to start 

 up again? When a grain of wheat be- 

 gins to sprout it shows growth, reproduc- 

 tion of cells by cell division, motion, and 

 the ordinary phenomena of irritability. 

 All these stop if (after 4 or 5 days of 

 growth) the seed be allowed to dry up 

 again. We can easily cause them to 

 start up once more by putting the seed 

 in water. Can we do the same with re- 

 spect to destructive metabolism, which 

 seems to be a process absolutely essential 

 to liie? 



If we stop the destructive metabolism 

 of the candle by a violent alteration of 

 its physical structure, as by smashing it 

 with a hammer, we cannot make it burn 

 again in the same way as before. Its 

 fragments may be burned but we shall 

 not get the same candle flame that we 

 had before. In the same way such an 

 organism as a seed may be shattered by 

 a blow and its fragments may go on burn- 



