Innumerable other instances of the same kind might be given;[73] but I have now said enough to establish the only points with which I am here concerned—namely, that gesture-language admits of being developed to a degree which renders it a fair substitute for spoken language, where the ideas to be conveyed are not highly abstract; and that it admits of being so developed without departing further from a direct or natural expression of ideation (as distinguished from a conventional or artificial) than allows it to be readily understood by the sign-talkers, without any preconcerted agreement as to the meanings to be attached to the particular signs employed. Such being the case, it is of importance next to note that, as all the existing races of mankind are a word-speaking race, we are not now able to eliminate this factor, and to say how far the sign-making faculty, as exhibited in the gesture-language of man, is indebted to the elaborating influence produced by the constant and parallel employment of spoken language. We can scarcely, however, entertain any doubt that the reflex influence of speech upon gesture must have been considerable, if not immense. Even the case of the deaf-mutes proves nothing to the contrary; for these unfortunate individuals, although not able themselves to speak, nevertheless inherit in their human brains the psychological structure which has been built up by means of speech; their sign-making _faculty_ is as well developed as in other men, though, from a physiological accident, they are deprived of the ordinary means of displaying it. Therefore we have no evidence to show to what level of excellence the sign-making faculty of man would have attained, if the race had been destitute of the faculty of speech. I shall have to return to this consideration in the next chapter, and only mention it here to avoid an undue estimate being prematurely formed of the importance of gesture as a means of thought-formation, or distinct from that of thought-expression. I shall now proceed to analyze in some detail the syntax of gesture-language. And here again I must depend for my facts upon the two writers who have best studied this kind of language in a properly scientific manner.