Smith, Educahihty of Param(£cium. 503 



as to react in these ways. The conditions are physical and the 

 thing's movements are physical. 'Is the adjustment somethingelse, 

 something half psychical } If it can be shown that a little mind 

 would help in making the movements, then we may busy ourselves 

 in describing the behavior of mind as it lends a helping hand to 

 clumsy protoplasm. But what seems unphysical is not the con- 

 traction but the purpose which the contraction serves. 



The purpose that some contractions serve is regulation or read- 

 justment and we may call behavior regulatory when a process hav- 

 ing proceeded too far is the cause of its own remedy. Such readjust- 

 ment is not without parallels in the world of inorganic manifolds. 

 For instance, I put my coffee pot on an open camp fire, the fire 

 becomes too hot, and the water boils over. But the boiling over 

 of the water regulates the fire so that a fire of nearly constant heat 

 is kept up as long as there is a certain amount of water in the pot. 

 So a pond is kept from freezing to the bottom in winter by a regu- 

 lation based on the densities of water at different temperatures. 

 As it changes from a temperature of 3.9° C. it becomes, up to a 

 certain point, less dense. Therefore, when the whole pond is at 

 a temperature of 3.9° and the top is cooled, the warmer water 

 from the bottom does not rise. So many machines have been 

 made involving a regulatory principle, such as the burglar alarm 

 or the differential valve, that no mystery surrounds it. 



There is a difference most valuable for classification between 

 living organisms, which through metabolism return after some 

 time to, or nearly to, the original state which existed previous to 

 an experience, and those inorganic manifolds which do not return 

 to a normal state but which remain indefinitey changed after they 

 are acted upon. It is this reversion to a normal state in all but the 

 highest nerve centers of living organisms which makes possible 

 their adaptation to often recurring stimuli of the same kind, and 

 the stability of those vital economies which we call adjustment 

 and adaptation. 



For instance, let an organism at birth be capable of giving N 

 reactions (<3, h, c, — N) to a definite stimulus S and let only one of 

 these reactions be appropriate. If only one reaction can be given 

 at a time and if the one given is determined by the state of the 

 organism at the time S is recevied, there is one chance in N that 

 it is the appropriate reaction. When the appropriate reaction is 

 finally given the other reactions are not called into play, S 



