Now, of the various forms of gesture-language, the one that is least subject to change is doubtless the means of communication employed by those who are bereft of hearing, and therefore of speech as well, namely, the _deaf and dumb_. A similar means of communication through signs and gestures may also be observed among peoples of low culture. Especially when they consist of tribes with markedly different dialects, do such peoples make use of gestures in communicating with one another. Investigations of the spontaneously arising gesture-language of deaf-mutes date largely from the first half of the nineteenth century. More recent studies have been made of the gestures of the North American Indian tribes, and similar, though less complete, observations have been reported concerning the Australians. In these cases, however, gestures sometimes serve also as a sort of secret language. This is even more true of certain signs that occur among some of the peoples of southern Europe, as, for example, among the Neapolitans. In considering the question before us, such cases must, of course, be excluded, since the motive of communicating ideas may here be entirely displaced by that of keeping them secret; instead of a language that arises spontaneously, we have a means which is, on the whole, consciously elaborated for purposes of mutual understanding. If we disregard these cases, which belong to an entirely different order of facts, and examine the data gathered from widely different parts of the earth and from very diverse conditions of culture, we find a remarkable agreement. In certain details, of course, there are differences. The ideas of the Indian are not in all respects like those of the civilized European or those of the Australian. Nevertheless, the gestures that refer to specific concrete objects are frequently so similar that many of the signs employed by the gesture-language of the deaf-mutes of Europe may be found among the Dakota Indians. Could we transfer one of these deaf and dumb persons to this group of Indians, he would probably have no difficulty at all in communicating with them. In more recent times the opportunity of investigating spontaneous gesture-language has not been so great, because deaf-mutes have become more and more educated to the use of verbal language. The principal material for the study of the natural gesture-language of deaf-mutes is, therefore, still to be found in the older observations of Schmalz (1838, 2nd ed. 1848), a German teacher of people thus afflicted, and in the somewhat later reports of an Englishman by the name of Scott (1870).