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mental act leaves in our physical and mental structure a 

 tendency to reproduce itself, and that whenever this repro- 

 duction occurs the tendency is thereby strengthened so 

 that a tendency often reproduced becomes almost automatic," 

 the least objectionable term for that which survives our 

 perceptions and ideas is probably that of residuum^ which 

 only indicates an unquestionable fact of our mental life. 

 Nay, more, it may be asserted that " the relation subsisting 

 between the actual perception and the residuum is the rela- 

 tion between the conscious and the unconscious," as between 

 these two worlds there must exist such a correlation that to 

 each mode of the one a mode of the other corresponds. 

 As Miiller says : " Forgetfulness means that the idea of a 

 thing is in equilibrium with other ideas, and recollection that 

 this idea quits the state of equilibrium, and enters the state 

 of motion. No idea is lost ; and every operation of the 

 mind, in virtue of which a latent idea passes to the active 

 state, is a state of recollection." 



Memory may also be regarded as a form of habit, for if in 

 tracing the evolution of mind we go " from instinct, which 

 is automatic, to reason, which is so no longer, we may say 

 that memory is the transition from perfect to imperfect 

 automatism. If we trace it in the reverse direction, then 

 memory indicates the moment when what was free and 

 conscious tends to become unconscious." Indeed, heredity 

 itself may be said to be a specific memory, being to the 

 species what memory is to the individual ; and the "heredity 

 of memory is implied in physiological heredity." Dr. 

 Maudsley says : " The permanent effects of a particular 

 virus, such as that of variola or syphilis, in the constitution, 

 shows that the organic element remembers, for the remainder 

 of its life, certain modifications it has received. The manner 



