Sensation 81 



stimuli than are the somatic cells, they carry 

 stimuli more easily and with less waste than 

 earlier growths. Nerve cells are germ cells 

 captured and turned to a new use. Their 

 differentiation is not due to the simple laws 

 of growth, but is the result of the pressure of 

 complex conditions. Were they free to assume 

 simpler forms, they would become independent 

 organisms instead of mere propagators of ac- 

 tivity generated elsewhere. Their passivity 

 is not a natural state, but is impressed upon 

 them by confinement. All cell aggregates are 

 primarily motor. They lose this function only 

 in an abnormal position. 



Herbert Spencer has said that the growth of 

 nervous power is opposed to reproduction, and 

 that the rate of production falls off as nervous 

 power increases. If the nerves are made up of 

 germ cells, the greater part of which are 

 retained and specialized, the organism has 

 less surplus energy to reproduce its kind. 

 Confined sex products thus become the means 

 by which currents are propagated. They are 

 more responsive and quicker conductors than 

 other cells, and motor energy passes along 



