By the "deaf" in the present study is meant that element of the population in which the sense of hearing is either wholly absent or is so slight as to be of no practical value; or in which there is inability to hear and understand spoken language; or in which there exists no real sound perception. In other words, those persons are meant who may be regarded as either totally deaf or practically totally deaf.[1] With such deafness there is not infrequently associated an inability to speak, or to use vocal language. Hence our attention may be said to be directed to that part of the community which, by the want of the sense of hearing and oftentimes also of the power of speech, forms a special and distinct class; and is known, more or less inaccurately, as the "deaf and dumb" or "deaf-mutes" or "mutes." In our discussion it is with deafness that we are primarily concerned. _Deafness_ and _dumbness_ are, physically, two essentially different things. There is no anatomical connection between the organs of hearing and those of speech; and the structure and functioning of each are such as to preclude any direct pathological relation. The number of the so-called deaf and dumb, moreover, who are really dumb is very small--so small actually as to be negligible. Almost all who are spoken of as deaf and dumb have organs of speech that are quite intact, and are, indeed, constructively perfect. It comes about, however, that dumbness--considered as the want of normal and usual locution--though organically separate from deafness, is a natural consequence of it; and does, as a matter of fact, in most cases to a greater or less extent, accompany or co-exist with it. The reason of this is that the deaf, particularly those who have always been so, being unable to hear, do not know how to use their organs of speech, and especially are unable to modulate their speech by the ear, as the hearing do. If the deaf could regain their hearing, they would have back their speech in short order. The character of the human voice depends thus on the ear to an unrealized degree. NUMBER OF THE DEAF IN THE UNITED STATES According to the census of 1900 there were 37,426 persons in the United States enumerated as totally deaf;[2] and according to that of 1910 there were 43,812 enumerated as "deaf and dumb."[3] Hence we may assume that there are between forty and fifty thousand deaf persons in the United States forming a special class.[4] The following table will give the number of the deaf in the several states and the number per million of population, according to the census of 1910.[5] NUMBER OF THE DEAF IN THE SEVERAL STATES NO. PER NO. PER MILLION OF MILLION OF NO. POPULATION NO. POPULATION