The mode in which words are learnt and extended may be studied most simply in the nursery. A child, say, has learnt to say _mambro_ when it sees its nurse. The nurse works a hand-turned sewing machine, and sings to it as she works. In the street the child sees an organ-grinder singing as he turns his handle: it calls _mambro_: the nurse catches the meaning and the child is overjoyed. The organ-grinder has a monkey: the child has an india-rubber monkey toy: it calls this also _mambro_. The name is extended to a monkey in a picture-book. It has a toy musical box with a handle: this also becomes _mambro_, the word being extended along another line of resemblance. A stroller with a French fiddle comes within the denotation of the word: a towel-rail is also called _mambro_ from some fancied resemblance to the fiddle. A very swarthy hunch-back _mambro_ frightens the child: this leads to the transference of the word to a terrific coalman with a bag of coals on his back. In a short time the word has become a name for a great variety of objects that have nothing whatever common to all of them, though each is strikingly like in some point to a predecessor in the series. When the application becomes too heterogeneous, the word ceases to be of use as a sign and is gradually abandoned, the most impressive meaning being the last to go. In a child's vocabulary where the word _mambro_ had a run of nearly two years, its last use was as an adjective signifying ugly or horrible. The history of such a word in a child's language is a type of what goes on in the language of men. In the larger history we see similar extensions under similar motives, checked and controlled in the same way by surrounding usage. It is obvious that to avoid error and confusion, the meaning or connotation of names, the concepts, should somehow be fixed: names cannot otherwise have an identical reference in human intercourse. We may call this ideal fixed concept the LOGICAL CONCEPT: or we may call it the SCIENTIFIC CONCEPT, inasmuch as one of the main objects of the sciences is to attain such ideals in different departments of study. But in actual speech we have also the PERSONAL CONCEPT, which varies more or less with the individual user, and the POPULAR or VERNACULAR CONCEPT, which, though roughly fixed, varies from social sect to social sect and from generation to generation.