THE GENESIS OF FUNCTIONAL INERTIA 121 



conditions ") by means of two properties which are, in 

 ultimate analysis, based on the particular inter-rela- 

 tion at any one moment between the two metabolic 

 states in the protoplasm. A stimulus may be almost 

 anything except a state of the molecules themselves. 



The stimulus is anything which causes or tends 

 to cause the molecules to rearrange themselves in 

 space or to be the means of transforming energy, 

 but the rearranging of the molecules and their 

 transforming of energy are not stimuli, but the 

 effects of stimuli. When phenomena are credited 

 to " internal stimuli," these metabolic transforma- 

 tions themselves are regarded as the stimuli, 



