688 Dynamic Theory. 



than one stimulation, and must have at least two, one of which modi- 

 fies the other. After the meeting of the direct stimuli at the common 

 point where their mutual interactions condense them into one, this one 

 stimulus goes forward as the purpose. A purposive action is therefore 

 at least one remove further from the direct stimulation of the environ- 

 ment than is a spinal reflex action, although depending upon the envi- 

 ronment just as much. The diagram fig. 370 will serve for illustration. 



a Q . ^ c a, 6, c. Reflex action. 



x, y. Sense organs. 

 , ff h. Brain cells. 

 $ c 1 . Ganglion, 

 fa ff. Simple automatic action. 



FIG. 370. 



It is evident that the purpose may be many removes from the original 

 stimuli, and may therefore be a very complicated affair, for the greater 

 its distance the greater the number of original stimuli which enter into 

 its make-up. It is not likely that in any complicated purpose all the 

 original stimuli are of equal weight*. Some one may be the main spring, 

 and the others only modifiers which simply regulate the time when the 

 action shall be performed, or the manner or the intensity of its per- 

 formance. 



FIG. 371. 



FIG. 371. Diagram of Purposive action. 



, x, y. Original stimuli. e First purposive action. 



b. Reflex cell. /.Modification of second degree, 



c. Simple reflex action. .(/.Second purposive action. 



d. First modification. A. Modification of third degree. 



i Third purpose. 



After two or more direct stimuli have entered into composition to dif- 

 ferentiate a common cell, such cell becomes a memory cell ; that is, a 

 subsequent stimulation of that cell will reproduce the manifestation of 

 the same sort of action which came from it in the first place. This being 

 the case, it is obvious that after the cells at d, fig. 371, have become es- 

 tablished, they no longer depend upon the original stimuli, but may be 

 restimulated by any one of them, or by some other associated stimulus. 

 After a man has once seen the state-house, he need not see it again in 

 order to describe it ; any associated stimulus can re-erect the memory 

 of it, which is then a power competent to liberate motor stimulation of 



