DEAF-MUTISM.
Definition. — Deaf - mutism, strictly speaking, signifies the abnormality which is characterized by the co-existence of deafness and dumbness. Various cir cumstances, which will be treated of in the following pages, necessitate, how ever, a more limited definition. Deaf mutism may, therefore, be defined as a pathological condition dependent upon an anomaly of the auditory organs, either congenital or acquired in early child hood, causing so considerable a diminu tion of the power of hearing as to pre vent the acquisition of speech, or— should speech have been acquired before the occurrence of the loss of hearing— as to prevent its preservation by the aid of hearing alone. Persons exhibiting this pathological condition are described as deaf-mutes, even when speech has been acquired by a special system of in struction.
Theoretically, deaf-mutism is an ill defined condition, which cannot be dis tinctly separated from other conditions related to it. This is a natural conse quence of its being a pathological term founded, not only upon a symptom, deaf ness, bit also upon the intensity of that symptom and the period of its occur rence. There is, also, an apparent con tradiction in the fact that deaf-mutes in clude, not only those who cannot. but, also, those who can, hear or speak. Prac tically, however, there is seldom any dif ficulty in determining whether a person is or is not a deaf-mute, just as it is, also, as a rule, easy to recognize deaf-mutism, when the subject in question has passed the first years of infancy. The reason is that the acquisition and preservation of speech in childhood is so dependent upon hearing that, as soon as the latter sinks below a certain degree, the former can not be developed, or is lost, and this secondary dumbness does not easily es cape observation. Occasionally, it may be difficult to decide whether a child should be described as a deaf-mute or as merely deficient in hearing and speak ing. Such cases must be decided by purely practical considerations, and it may not be out of the way to observe that in Denmark—one of the few coun tries where the education of deaf-mutes is compulsory—all children are consid ered deaf-mutes who cannot, owing to their deficient hearing, take part in the instruction given to normal children.
Classification. — Deaf-mutism can be classified (1) either according to the de gree of its symptoms, or (2) according to its etiology. In the first case a distinc tion must be made according as the deaf ness or dumbness is absolute or not. True may be described as being the state in which the hearing is posi tively nil, and in which there is no power of speech, unless it be acquired by a special method of instruction. Persons with this form of deafness may be desig nated as true deaf-mutes. Those who have some slight power of hearing or some power of speech (either because the hearing is not totally absent or because the deafness occurred after speech had been acquired) may be described as semi mutes.
Etiologically, deaf-mutism has been further divided into endemic (i.e., that which attaches to certain dis tricts and their natural conditions) and sporadic (which is the re sult of certain accidental causes).
The most general classification of deaf mutism is that which discriminates be the cases of deaf-mutism are caused by acquired deafness. The relative propor tion must, however, vary very much in different places and at different periods, epidemics of certain infectious diseases, for instance, increasing the absolute number of deaf-mutes with acquired tween the deaf-mutism resulting from congenital pathological changes of the or gans of hearing and that resulting from such changes which are acquired after birth.
We have reason to surmise, according to modern statistics, that at least half deafness. Future investigations will, peigl haps, prove that acquired deafness has a' still greater preponderance in the causa tion of deaf-mutism than we are at pres ent authorized in believing.