32 Living and Dead Matter and 



and every two days a few cells from the margin of 

 the piece have to be transferred to a new culture 

 medium. 



This effect of lack of oxygen explains also why the 

 immortality of the somatic cells is not obvious. Death 

 in a human being consists in the stopping of heart 

 beat and respiration, which also terminates the action 

 of the brain or at least of consciousness. Immediately 

 after the cessation of heart beat and respiration the cells 

 of muscle and of the skin and probably many or most 

 other organs are still alive and might continue to live 

 if transferred to another body with circulation and 

 respiration. As a consequence of the lack of oxygen 

 supply in the dead body they will, however, die com- 

 paratively rapidly. It may be stated that hearts taken 

 out of the body after a number of hours can still beat 

 again when put into the proper solutions and upon 

 receiving an adequate oxygen supply. 



The idea that the body cells are naturally immiortal 

 and die only if exposed to extreme injuries such as 

 prolonged lack of oxygen or too high a temperature 

 helps to make one problem more intelligible. The 

 medical student, who for the first time realizes that 

 life depends upon that one organ, the heart, doing its 

 duty incessantly for the seventy years or so allotted to 

 man, is amazed at the precariousness of our existence. 

 It seems indeed uncanny that so delicate a mechanism 

 should function so regularly for so many years. The 



