Persons who are deaf and dumb are generally unable to speak in consequence of being unable to hear, which prevents their learning the significance of vocal sounds, although the vocal apparatus may be perfectly developed. Persons may be born deaf in consequence of imperfect development of the organs of hearing, or of disease of the ear previous to birth. In many cases, deafness is the result of diseases occurring in infancy or early childhood. It is not necessary that hearing should be entirely destroyed to produce deaf-mut-ism, as a considerable degree of impairment of hearing will often privent a child from making the necessary attempts to learn to speak. It is thought that the marriage of persons nearly related, is a frequent cause of deaf-mutism, as it has been supposed to be of idiocy.

The Treatment of Deafness - Mutism

Although in these cases there is no call for treatment for the purpose of restoring the hearing, there is an imperative necessity for the employment of proper measures by means of which the condition of these unfortunate individuals may be ameliorated. The experience of numerous deaf and dumb asylums in this and other countries has shown beyond question that deaf mutes are capable of a high degree of mental culture and such a course of training as will render them able to compote with their more fortunate fellows in the various departments of life. Educated mutes are able to communicate readily with each other by means of the "sign language," a sort of natural mode of speech which is in common use among the North American Indians and other savage tribes. Attention was first called to this mode of mute speech through its use by two deaf mute sisters

Figs. 467 to 494. Sign Language Chart.

Figs. 467 to 494. Sign Language Chart.

It has been improved and perfected, until it admits of great fluency of expression and is capable of expressing ideas with sufficient rapidity to follow very closely an ordinary speaker. Educated mutes usually make use, to a greater or less extent, of the manual alphabet, by means of which words may be readily spelled out. The greatest advance in the instruction of the deaf and dumb, has been through the discovery that mutes can be taught to understand spoken language by carefully watching the movements of the lips and throat, and can also become able to speak by imitating the movements by which various sounds are produced. This is known as the "German method." A successful attempt has been made to illustrate the various sounds of speech by means of symbols termed "visible speech," a few illustrations of which are given in Fig. 494.