Should the results of such experiments be negative, it is not necessary, as before mentioned, to conclude that the child will become a deaf-mute. After the com pletion of the first year of infancy, how ever, the older the child, the greater the importance which must be attached to such negative results. After that period we may look for another symptom to help us in our diagnosis, viz.: the ab sence of speech. This, too, may be de lusive, as some children, although in full possession of normal powers of hearing and intellect, do not begin to speak at the end of their first year, but later, some times much later. The cause may be some hidden condition or constitutional disease; for instance, rickets.
Another condition which may be mis taken for deaf-mutism is simple mutism (aphasia) uncomplicated with deafness or idiocy. This abnormality, which is not at all rare in adults as the result of cer tain brain diseases, is but seldom con genital or acquired in infancy, at least, there are but few references to it in lit erature. This form of aphasia must, ac cording to some authors, be regarded as the result of a disease which is localized in the central nervous system, causing total inability of speech in the person affected, or inability to speak more than a few indistinct words. This infantile aphasia, which seems, as a rule, to be congenital, differs from the mutism of deaf-mutism, principally inasmuch as it is not accompanied by deafness, and often, also, in the subject affected being able to produce certain words or sounds resembling words, which are always em ployed in attempts at speech. Aphasia accompanying feeble-mindedness, imbe cility, or idiocy is a much more frequent abnormality, which is still more easily mistaken for deaf-mutism, especially in such cases where the imbecility is so con siderable that the interest for sound is diminished. In these cases, however, the imbecility, which must be regarded as the primary disease, will generally shovr itself in the patient's appearance, move ments, gestures, etc.
Hysterical mutism may sometimes simulate deaf-mutism. It is, however, generally accompanied by pronounced symptoms of hysteria, and exhibits itself by the patient's mak-lug- no attempts to speak, or even to articulate. It is gener ally of short duration and easily recog nized, the diagnosis only offering some difficulty in cases where the mutism ap pears in deaf, hysterical subjects.
The question whether deaf-mutism is congenital or acquired is, doubtless, that which offers the greatest difficulty in forming a diagnosis of deaf-mutism. In all cases, however, when the deafness ap pears after the child has begun to speak, or where the immediate causes of deaf ness are known, the diagnosis is an easy matter. If, on the contrary, the deaf ness has made its appearance prior to the period at which speech is generally de veloped—whether the morbid changes of the organs of hearing causing deafness are congenital or acquired—a decision as to the fcetal or post-fcetal origin of the deafness is accompanied by great, indeed often insurmountable, difficulties. In such cases it is, therefore, of the greatest moment to obtain the most explicit in formation from the deaf-mute's friends, especially the parents, who are most likely to be able to give reliable informa tion as to the diseases and pathological conditions which exist in the family. An
opinion as to the origin of deaf-mutism can, as has been previously mentioned, only in exceptional eases be based upon objective examination of the subject. Such exceptional cases are, for instance, those in which visible and pronounced malformations of that part of the ear which is accessible to examination clearly indicate that deaf-mutism is the result of congenital changes of the auditory organs. Such cases are, however, very rare. Malformations in other parts of the body also indicate, though with a much less degree of certainty, that the condition in the ear is congenital; but these cases are rare. The objective ex amination of the ear, in the great ma jority of cases, offers nothing which can be relied upon with any degree of cer tainty, since, on the one hand, patholog ical changes of the external and middle ear, which may, according to their na ture, be acquired after birth, may very well exist in persons whose deafness is due to congenital malformations of the auditory organ; while, on the other hand, less-pronounced congenital changes of the external and middle ear (for in stance, lesser degrees of microtia and ma crotia, contraction of the external meatus, abnormal position of the drum head, etc.) may very well appear in per sons with acquired deafness.
A final decision as to the congenital or acquired origin of a case of deaf-mut ism must, then, in the majority of cases, be entirely based upon inquiry, and, even when explicit information is obtainable, it is often difficult to arrive at a definite opinion. It will be always advisable to make inquiries whether the child's speech has developed in the same way as that of ordinary children of the same age, because non-professional persons' statements as to a child's power of hear ing are often unreliable. Should the answers be in the affirmative, and should it be proved that the power of speech has been lost, or is arrested in its devel opment from some or other cause (acute brain disease, scarlet fever, measles, etc.), it may be safely concluded that the deaf mutism is of post-fcetal origin. This diagnosis is also justified, though with less certainty, when the above-mentioned causes have shown themselves during the first years of infancy, unless, of course, ample and satisfactory proof can be pro duced that the child has never possessed the power of hearing, or that the more remote causes of deaf-mutism (unfavor able social conditions, heredity, consan guinity, etc.) have appeared in great force; in such cases a decision must re main doubtful. Should, however, the possibility of the direct causes (scarlet fever, brain diseases, measles, etc.) be excluded, and it is proved that the child never possessed the power of speech, it may be supposed that the deaf-mutism is the result of congenital changes of the organs of hearing. This supposition is the more warranted the greater proof there is that the more remote causes of deaf-mutism have played their part in the case in question.
Etiology.—The causes of deaf-mutism may be subdivided into two groups: (A) the remote causes, and (B) the immediate causes.