from one another in a greater or less degree, and some of them, at least, we know by historical evidence to be descendants of a common original. This state of things finds its ready and simple explanation in the principles which have been already laid down; they will demand, therefore, but a brief application and further illustration.
We have been speaking, when treating of the growth of language, of vital processes, as going on in the body of speech itself, like the process of fermentation in bread, or of the displacement and replacement of tissues in an animal organism. But we have been careful, at the same time, to bear in mind that the word "process" was thus used only in a figurative sense. Every item of change which goes to make up the growth of human speech is ultimately a result of the conscious effort of human beings. In language, the atoms which compose the fermenting mass and the growing tissue are not inert matter, acted on by laws of combination and affinity, but intelligent creatures, themselves acting for a purpose. A process of linguistic growth, then, is only the collective effect, in a given direction, of the acts of a number of separate individuals, guided by the preferences, and controlled by the assent, of the community of which those individuals form a part. And upon the joint and reciprocal action on language of the individual and the community depend all the phenomena of dialectic separation and coalescence.
For, in the first place, it is evident that the infinite diversity of character and circumstance in the intelligent beings who have language in charge must tend to infinite diversity in their action and its products. Each independent mind, working unrestrainedly according to its own impulses, would impress upon the development of speech a somewhat different history. It was shown almost at the beginning of our discussions (p. 22) that no two men speak exactly the same tongue: of course, then, they would not propagate the same. Each has his own vocabulary, his own pet words and phrases, his own deviations from the normal standard of pronunciation, of construction, of grammar; the needs of each are in some degree unlike those of others; his mind is somewhat differ-
