xxxiv.] MENTAL GROWTH. 87 



Further ; the gi'eater part of our mental acquisitions does 

 not consist of mental pictures of single objects, or mental 

 representations of particular events. Such pictures and 

 such representations are not formed until memory develops 

 into the power of recollection, and it is not probable that 

 animals or young children form them at all. The most 

 important mental acquisitions, and those the accumulation 

 of which constitutes the rapid mental growth of young 

 children, do not consist of the residua^ of single impres- Coales- 

 sions, but of the coalesced residua of many impressions. ^^^9^: °^, 



_•'•'■ residua by 



An impression leaves its residuum in the memory ; and forgettiug. 

 when it is often repeated, the residua of the several im- 

 pressions become inseparable and indistinguishable, and 

 coalesce into one. It is in this way that we become 

 familiar with the words of our own language, and with 

 everything else that is familiar ; indeed, it is part of tlie 

 definition of familiarity, that we are not familiar with what con. 

 anything until we have forgotten how often we have ^.*^''"*5^ 

 witnessed it. The earliest, the most durable, and the most arity. 

 important of our mental acquisitions are of this kind. 

 The best instance of this is, perhaps, our knowledge of our 

 own language. We have become familiar with words in 

 common use, not by hearing them once, but by hearing 

 them oftener than we can remember ; our knowledge of any 

 common word is not a single residuum from the impression 

 made by hearing it once, but a coalesced residuum, con- 

 sisting of the indistinguishably united residua that have 

 been left at each time we have heard it. Familiarity with 

 a word consists of two elements, familiarity with its sound 

 and familiarity with its meaning. The sound of a word is 

 only an impression on the sense of hearing, but the know- 

 ledge of the meaning consists of a mental association, 

 effected in virtue of the law of habit, between the sound 

 and the thing which it signifies. In order that language Words 

 should rightly fulfil its function of communicating thought, ™|Jy "°* 

 it is necessary that every word shall suggest its meaning ; suggest 



1 I borrow the word "residuum" from " Morell's Mental Philosophy." 

 He has borrowed it from the Gorman writers on psychology. I make no 

 apology for the use of a most courenieut though new word. 



