Language is rooted half in the bodily and half in the mental nature of
man. The vocal sounds which form the raw materials of language could not
be produced without a peculiar conformation of the organs of speech; the
enunciation of duly accented syllables would be impossible without
the nicest coordination of the action of the muscles which move these
organs; and such co-ordination depends on the mechanism of certain
portions of the nervous system. It is therefore conceivable that the
structure of this highly complex speaking apparatus should determine a
man's linguistic potentiality; that is to say, should enable him to use
a language of one class and not of another. It is further conceivable
that a particular linguistic potentiality should be inherited and become
as good a race mark as any other. As a matter of fact, it is not proven
that the linguistic potentialities of all men are the same.