the origin of sign language through its connection with that of oral
speech. In this examination it is essential to be free from the vague
popular impression that some oral language, of the general character
of that now used among mankind, is "natural" to mankind. It will be
admitted on reflection that all oral languages were at some past time
far less serviceable to those using them than they are now, and as
each particular language has been thoroughly studied it has become
evident that it grew out of some other and less advanced form. In
the investigation of these old forms it has been so difficult to
ascertain how any of them first became a useful instrument of
inter-communication that many conflicting theories on this subject
have been advocated.

Oral language consists of variations and mutations of vocal sounds
produced as signs of thought and emotion. But it is not enough that
those signs should be available as the vehicle of the producer's own
thoughts. They must be also efficient for the communication of such
thoughts to others. It has been, until of late years, generally held
that thought was not possible without oral language, and that, as man
was supposed to have possessed from the first the power of thought, he
also from the first possessed and used oral language substantially
as at present. That the latter, as a special faculty, formed the
main distinction between man and the brutes has been and still is
the prevailing doctrine. In a lecture delivered before the British
Association in 1878 it was declared that "animal intelligence is
unable to elaborate that class of abstract ideas, the formation of
which depends upon the faculty of speech." If instead of "speech" the
word "utterance" had been used, as including all possible modes of
intelligent communication, the statement might pass without criticism.
But it may be doubted if there is any more necessary connection