64 GENERAL VIEW AND BASIS OF SCIENTIFIC RESEARCH. 



Memory is potential cerebral impression. The possi- 

 bility of it appears to depend essentially upon physical 

 changes produced by impressions in the cortical layers of 

 the cerebrum; and the amount of this change appears 

 to be greatest with those impressions which are the most 

 vivid and the most firmly fixed. That memory is due to 

 such organic change and aptitude is shown by the fact 

 that sometimes ideas which have been entirely forgotten 

 are recalled by the action of disease or other excitemerit 

 of the brain ; and that it depends upon the state of the 

 brain, and upon all bodily conditions that affect that 

 organ, is shown by abundance of evidence. 6 It may be 

 questioned whether impressions are really left upon our 

 minds by anything else than ideas;' 1 and this is in 

 accordance with the fact that we cannot as distinctly 

 remember pain itself as the idea that we suffered it, and 

 that the memory of an object is generally very much less 

 vivid than the sensation produced by the object itself. We 

 also usually grow much more quickly out of remembrance 

 of sensations than out of that of ideas, partly, however, in 

 consequence of the latter being more frequently repeated. 

 It is probably owing to an action or property of nervous 

 matter analogous to elasticity that the permanent idea 

 immediately resulting from a sensation and impression is 

 feebler than the sensation itself. 



The more purely physical the impression, the less is 

 it usually retained in the memory. Our remembrance 

 of great physical pain or pleasure is extremely inadequate ; 

 that of tastes is less permanent than that of sounds, and 

 of sounds less than of sights. Sight is also the most 

 refined sense, and yields the least palling, the purest and 

 most enduring of sensational enjoyments ; but our me- 



1 Carpenter's Mental Physiology, p. 431. 



