248 JOSEPH JOHN MURPHY ON EVOLUTION IN LANGUAGE. 
been formed by the voluntary and conscious activity of the mind in 
comparing. But the impression of a single familiar word on the 
memory,—which, I think, is properly called a concept,— does appear 
to consist of the impressions made on the mind by the countless 
number of times it has been heard, which impressions have coalesced 
into one by a process comparable to the formation of a composite 
photograph, without any higher mental activity than is implied in 
all remembered sensation. 
