On Memory. 497 
vividly to the mind than another seen but once, and why 
things that have been seen are usually remembered more 
distinctly than those that have been only imagined. 
“ Old men are defective in memory, and cannot learn any- 
thing without much difficulty, because they want animal 
spirits to make new traces, and because the fibres of the 
brain have become too hard to receive, or too moist to 
retain, such impressions. For the same reason they who 
learn with the greatest ease forget the soonest ; in regard 
when the fibres are soft and flexible objects make a slight 
impression, which the continual course of animal spirits 
easily wears off. On the contrary, the fibres of those who 
learn slowly, being less flexible and less subject to be 
shaken, the traces are more deeply engraven, and last the 
longer, from all which observations it follows that the 
memory is absolutely dependent on the body being im- 
paired or strengthened, according to the changes which 
befall that body,—a fall, a fever, &c., being frequently 
found to erase or blot out all traces, to bear away all the 
ideas, and to cause an universal forgetfulness.” 
The chief difficulty that embarrasses this doctrine of 
memory is to conceive how such a great number of things 
and events as the brain is stored or filled with should be 
arranged in such order in the memory as that the one 
should not efface the other, and how in such a multitudi- 
nous assemblage of traces impressed on the brain, the 
animal spirits should call up or awaken those that the 
mind has occasion for. 
Again, it may be concluded that impressions once made 
on the brain or memory are never entirely lost, for although 
after inflammation of the brain and fever attended with 
cerebral symptoms, the memory is sometimes temporarily 
obscured, and the understanding lost, yet everyone’s expe- 
rience has taught him how often things and circumstances, 
apparently forgotten, have been recalled to the memory and 
mind by accidental associations which seem to have no 
other connection with them, and doubtless many have lis- 
tened with sorrow to the ravings of delirious persons, from 
whose lips have fallen expressions and relations which were 
evidently revelations of the real incidents of past and mis- 
spent time; and others may have heard with delight and 
surprise words of purest love given utterance to by the 
voice of maiden innocence, which were surely the tran- 
script of thoughts and ideas which had been in time of 
