Disturbances.

The organ of hearing is injured _at its peripheral extremity_, or else
the acusticus in its course; then occurs _difficulty of hearing_ or
_deafness_. What is spoken is not correctly heard or not heard at all:
the utterance is correct only in case the lesion happened late. If it
is inborn, then this lack of speech, alalia, is called _deaf-mutism_,
although the so-called deaf and dumb are not in reality dumb, but only
deaf. If words spoken are incorrectly heard on account of acquired
defects of the peripheral ear, the patient mis-hears, and the abnormal
condition is called paracusis.

(2) Central Disturbances.

_a._ The higher impressive central paths are disturbed: _centro-sensory
dysphasia and aphasia_, or _word-deafness_. Words are heard but not
understood. The hearing is acute. "Patients may have perfectly correct
ideas, but they lack the correct expression for them; not the thoughts
but the words are confused. They would understand the ideas of others
also if they only understood the words. They are in the position of
persons suddenly transported into the midst of a people using the same
sounds but different words, which strike upon their ear like an
unintelligible noise." (Kussmaul.) Their articulation is without defect,
but what they say is unintelligible because the words are mutilated and
used wrongly. C. Wernicke discovered this form, and has separated it
sharply from other disturbances of speech. He designated it sensory
aphasia. Kussmaul later named this abnormal condition word-deafness
(surditas verbalis).

_b._ The connections between the impressive sound-centers and the motor
speech-center are injured. Then we have intercentral conductive
dysphasia and aphasia. What is spoken is heard and understood correctly
even when _v_ is completely interrupted. The articulation is not
disturbed, and yet the patient utters no word of himself. He can,
however, read aloud what is written. (Kussmaul.) The word that has just
been read aloud by the patient can not be repeated by him, neither can
the word that has been pronounced to him; and, notwithstanding this, he
reads aloud with perfect correctness. In this case, then, it is
impossible for the patient of his own motion, even if the memory of the
words heard were not lost, to set in activity the expressive mechanism
of speech, although it might remain uninjured.

_c._ The motor speech-center is injured. Then we have centro-motor
dysphasia and aphasia