CHAPTER XV 



THE DISTRIBUTION OF ASSOCIATIVE MEMORY 

 IN THE ANIMAL KINGDOM 



i. The most important problem in the physiology 

 of the central nervous system is the analysis of the 

 mechanisms which give rise to the so-called psychic 

 phenomena. The latter appear, invariably, as a func- 

 tion of an elementary process, namely, the activity of 

 the associative memory. By associative memory I 

 mean the two following peculiarities of our central 

 nervous system : First, that processes which occur 

 there leave an impression or trace by which they can 

 be reproduced even under different circumstances 

 than those under which they originated. This pecu- 

 liarity can be imitated by machines like the phono- 

 graph. Of course, we have no right to assume that 

 the traces of processes in the central nervous system 

 are analogous to those in the phonograph. The sec- 

 ond peculiarity is, that two processes which occur 

 simultaneously or in quick succession will leave traces 

 which fuse together, so that if later one of the pro- 

 cesses is repeated, the other will necessarily be re- 

 peated also. The odour of a rose will at the same 



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