[Ill.u.s.tration: FIG. 1.]
The peripheral ear _o_, with the terminations of the auditory nerve, is by means of sensory fibers _a_, that are connected with the auditory nerve, in connection with the storehouse of sound-impressions, K. This is connected by means of the intercentral paths _v_ with the motor speech-center M. From it go out special fibers of communication, _h_, to the motor nerves of speech which terminate in the external instruments of articulation, _z_.
The impressive nerve-path, _o_ _a_ K, is centripetal; the expressive, M _h_ _z_, centrifugal; _v_, intercentral.
When the normal child learns to speak, _o_ receives the sound-impressions; by _a_ the acoustic-nerve excitations are pa.s.sed along to K, and are here stored up, every distinctly heard sound (a tone, a syllable, a word) leaving an impression behind in K. It is very remarkable here that, among the many sounds and noises that impress themselves upon the portions of the brain directly connected with the auditory nerve, a selection is made in the sound-field of speech, K, since all those impressions that can be reproduced, among them all the acoustic images necessary for speech, are preserved, but many others are not, e. g., thunder, crackling. Memory is indistinct with regard to these. From K, when the sound-images or sound-impressions have become sufficiently strong and numerous, the nerve-excitement goes farther through the connecting paths _v_ to M, where it liberates motor impulses, and through _h_ sets in activity the peripheral apparatus of speech, _z_.
Now, speech is disturbed when at any point the path _o_ _z_ is interrupted, or the excitation conducted along the nerve-fibers and ganglionic cells upon the hearing of something spoken or upon the speaking of something represented in idea (heard inwardly) is arrested, a thing which may be effected without a total interruption of the conduction, e. g., by means of poison and through anatomical lesions.
On the basis of these physiological relations, about which there is no doubt, I divide, then, all pure disturbances of speech, or _lalopathies_, into three cla.s.ses:
(1) Periphero-Impressive or Perceptive 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 p.r.o.nounced 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. If the center is completely and exclusively disturbed, then it is a case of pure ataxic aphasia. Spontaneous speaking, saying over of words said by another, and reading aloud of writing, are impossible. (Kussmaul.) On the other hand, words heard are understood, although the concepts belonging with them can not be expressed aloud. The verbal memory remains; and the patient can still express his thoughts in writing and can copy in writing what he reads or what is dictated to him.
(3) Periphero-Expressive or Articulatory Disturbances.
The centrifugal paths from the motor speech-center to the motor nerves of speech and to their extremities, or else these nerves themselves, are injured. Then occurs _dysarthria_, and, if the path is totally impa.s.sable at any place, _anarthria_. The hearing and understanding of words are not hindered, but speaking, repeating the words of others, and reading aloud are, as in the last case (2, _c_), impossible. In general this form can not be distinguished from the foregoing when both are developed in an extreme degree, except in cases of peripheral dysarthria, i. e., dyslalia, since, as may be easily understood, it makes no difference in the resulting phenomena whether the motor center itself is extirpated or its connections with the motor outlet are absolutely cut off just where the latter begins; but if this latter is injured nearer to the periphery, e. g., if the hypoglossus is paralyzed, then the phenomena are different (paralalia, mogilalia).
Here belongs all so-called mechanical dyslalia, caused by defects of the peripheral speech-apparatus.
Of these five forms each occurs generally only in connection with another; for this reason the topical diagnosis also is often extraordinarily difficult. But enough cases have been accurately observed and collected to put it almost beyond a doubt that each form may also appear for a short time purely by itself. To be sure, the anatomical localization of the impressive and expressive paths is not yet ascertained, so that for the present the centripetal roads from the acusticus to the motor speech-center, and the intercentral fibers that run to the higher centers, are as much unknown as the centrifugal paths leading from them to the nuclei of the hypoglossus; but that the speech-center discovered by Broca is situated in the posterior portion of the third frontal convolution (in right-handed men on the left, in left-handed on the right) is universally acknowledged.
Further, it results from the abundance of clinical material, that the acoustic-center K must be divided into a sound-center L, a syllable-center S, a word-center W, each of which may be in itself defective, for cases have been observed in which sounds were still recognized and reproduced, but not syllables and words, also cases in which sounds and syllables could be dealt with but no words; and, finally, cases in which all these were wanting. The original diagram is thereby considerably complicated, as the simple path of connection between K and M has added to it the arcs L S M and L S W M (Fig. 2).
[Ill.u.s.tration: FIG. 2.]
The surest test of the perfect condition of all the segments is afforded by the repet.i.tion of sounds, syllables, and words p.r.o.nounced by others.
Syllables and sounds, but no words, can be p.r.o.nounced if W is missing or the path S W or W M is interrupted; no syllables if S is missing or L S or S M is interrupted. If L is missing, then nothing can be repeated from hearing. If L M is interrupted, then syllables and words are more easily repeated than simple sounds, so far as the latter are not syllables. If L S is interrupted, then simple sounds only can be repeated. All these abnormal states have been actually observed. The proofs are to be found in Kussmaul"s cla.s.sic work on the disturbances of speech (1877). Even the strange case appears in which, L M being impracticable, syllables are more easily repeated than simple sounds.
If _a_ is interrupted before the acquirement of speech, and thus chronic deafness is present in very early childhood, articulation may still be learned through visual and tactile impressions; but in this case the sound-center L is not developed. Another, a sound-touch-center, comes in its place in deaf-mutes when they are instructed, chiefly through the tactile sensations of the tongue; and, when they are instructed in reading (and writing), a sound-sight-(or letter) center. This last is, on the contrary, wanting to those born blind; and both are wanting to those born blind and deaf. Instead is formed in them through careful instruction, by means of the tactile sensations of the finger-tips, a center for signs of sound that are known by touch (as with the printed text for the blind).
Accordingly, the eye and ear are not absolutely indispensable to the acquirement of a verbal language; but for the thorough learning of the verbal language in its entire significance both are by all means indispensable. For, the person born blind does not get the significance of words pertaining to light and color. For him, therefore, a large cla.s.s of conceptions, an extensive portion of the vocabulary of his language, remains empty sound. To the one born deaf there is likewise an extensive district of conceptions closed, inasmuch as all words pertaining to tone and noise remain unintelligible to him.
Moreover, those born blind and deaf, or those born blind and becoming deaf very early, or those born deaf and becoming blind very early, though they may possess ever so good intelligence, and perhaps even learn to write letters, as did the famous Laura Bridgman, will invariably understand only a small part of the vocabulary of their language, and will not articulate correctly.
Those born deaf are precisely the ones that show plainly how necessary hearing is for the acquirement of perfectly articulate speech. One who is deaf from birth does not even learn to speak half a dozen sounds correctly without a.s.sistance, and the loss of speech that regularly follows deafness coming on in children who have already learned to speak, shows how inseparably the learning and the development of perfect articulation are bound up with the hearing. Even the deafness that comes on in maturer years injures essentially the agreeable tone, often also the intelligibility, of the utterance.
2. The Organic Conditions of Learning to Speak.
How is it, now, with the normal child, who is learning to speak? How is it as to the existence and practicability of the nervous conduction, and the genesis of the centers?
In order to decide these questions, a further extension of the diagram is necessary (Fig. 3).
[Ill.u.s.tration: FIG. 3.]
For the last diagram deals only with the hearing and p.r.o.nouncing of sounds, syllables, and single words, not with the grammatical formation and syntactical grouping of these; there must further be a center of higher rank, the _dictorium_, or center of diction (Kussmaul), brought into connection with the centers L S and W. And, on the one hand, the word-image acquired (by hearing) must be at the disposition of the diction-center, an excitation, therefore, pa.s.sing from W to D (through _m_); on the other hand, an impulse must go out from the diction-center to p.r.o.nounce the word that is formed and placed so as to correspond to the sense (through _n_). The same is true for syllables and sounds, whose paths to and from are indicated by _k_ and _l_, as well as by _g_ and _i_. These paths of connection must be of twofold sort. The excitement can not pa.s.s off to the diction-center D on the same anatomical path as the return impulse from D, because not a single case is known of a nerve-fiber that in natural relations conducts both centrifugally _and_ centripetally, although this possibility of double conduction does occur under artificial circ.u.mstances. Apart, then, from pathological experience, which seems to be in favor of it, the separation of the two directions of the excitement seems to be justified anatomically also. On the contrary, it is questionable whether the impulse proceeding from D does not arrive directly at the motor speech-center, instead of pa.s.sing through W, S, or L. The diagram then represents it as follows (Fig. 4). Here the paths of direct connection _i_, _l_, and _n_ from D to M represent that which was just now represented by _i_ L _d_ and _l_ S _e_ and _n_ W _f_, respectively; in Fig. 4, _i_ conducts only sound-excitations coming from L, _l_ only excitations coming from S, and _n_ only those coming from W, as impulses for M. For the present, I see no way of deciding between the two possibilities. They may even exist both together. All the following statements concerning the localization of the disturbances of speech and the parallel imperfections of child-speech apply indifferently to either figure; it should be borne in mind that the nerve-excitement always goes _only_ in the direction of the arrows, never in the opposite direction, through the nervous path corresponding to them. Such a parallel is not only presented, as I have found, and as I will show in what follows, by the most superficial exhibition of the manifold deviations of child-speech from the later perfect speech, but is, above all, necessary for the answering of the question: what is the condition of things in learning to speak?
[Ill.u.s.tration: FIG. 4.]
3. Parallel between the Disturbances of Speech in Adults and the Imperfections of Speech in the Child.
In undertaking to draw such a parallel, I must first of all state that in regard to the pathology of the subject, I have not much experience of my own, and therefore I rely here upon Kussmaul"s comprehensive work on speech-disturbances, from which are taken most of the data that serve to characterize the individual deviations from the rule. In that work also may be found the explanations, or precise definitions, of almost all the names--with the exception of the following, added here for the sake of brevity--skoliophasia, skoliophrasia, and palimphrasia. On the other hand, the statements concerning the speech of the child rest on my own observations of children--especially of my own son--and readers who give their attention to little children may verify them all; most of them, indeed, with ease. Only the examples added for explaining mogilalia and paralalia are taken in part from Sigismund, a few others from Vierordt.
They show more plainly (at least concerning rhotacism) than my own notes, some imperfections of articulation of the child in the second year, which occur, however, only in single individuals. In general the defects of child-speech are found to be very unequally distributed among different ages and individuals, so that we can hardly expect to find all the speech-disturbances of adults manifested in typical fashion in one and the same child. But with very careful observation it may be done, notwithstanding; and when several children are compared with one another in this respect, the a.n.a.logies fairly force themselves upon the observer, and there is no break anywhere.
The whole group into which I have tried to bring in organic connection all the kinds of disturbances and defects of speech in systematic form falls into three divisions:
1. Imperfections not occasioned by disturbance of the intelligence--pure speech-disturbances or _lalopathies_.
2. Imperfections occasioned solely by disturbances of the intelligence--disturbances of continuous speech or discourse (Rede)--_dysphrasies_.
3. Imperfections of the language of gesture and feature--_dysmimies_.
I. LALOPATHY.
A. THE IMPRESSIVE PERIPHERAL PROCESSES DISTURBED.
_Deafness._--Persons able to speak but who have become deaf do not understand what is spoken simply because they can _no longer_ hear. The newly born do not understand what is spoken because they can _not yet_ hear. The paths _o_ and _a_ are not yet practicable. All those just born are deaf and dumb.
_Difficulty of Hearing._--Persons who have become hard of hearing do not understand what is spoken, or they misunderstand, because they _no longer_ hear distinctly. Such individuals easily hear wrong (paracusis).
Very young infants do not understand what is spoken, for the reason that they do _not yet_ hear distinctly; _o_ and _a_ are still difficult for the acoustic nerve-excitement to traverse. Little children very easily hear wrong on this account.
B. THE CENTRAL PROCESSES DISTURBED.
_Dysphasia._--In the child that can use only a small number of words, the cerebral and psychical act through which he connects these with his ideas and gives them grammatical form and syntactical construction in order to express the movement of his thought is _not yet_ complete.
(1) The Sensory Processes centrally disturbed.
_Sensory Aphasia_ (Wernicke), _Word-Deafness_ (Kussmaul).--The child, in spite of good hearing and sufficiently developed intelligence, can _not yet_ understand spoken words because the path _m_ is not yet formed and the storehouse of word images W is still empty or is just in the stage of origination.
_Amnesia, Amnesic Dysphasia and Aphasia, Partial and Total Word-Amnesia, Memory-Aphasia._--The child has as yet no word-memory, or only a weak one, utters meaningless sounds and sound-combinations. He can _not yet_ use words because he does not yet have them at his disposal as acoustic sound-combinations. In this stage, however, much that is said to him can be repeated correctly in case W is pa.s.sable, though empty or imperfectly developed.
(2) The Sensori-motor Processes of Diction disturbed.
_Acataphasia_ (Steinthal).--The child that has already a considerable number of words at his disposal is _not yet_ in condition to arrange them in a sentence syntactically. He can _not yet_ frame correct sentences to express the movement of his thought, because his diction-center D is still imperfectly developed. He expresses a whole sentence by a word; e. g., _hot!_ means as much as "The milk is too hot for me to drink," and then again it may mean "The stove is too hot!"
_Man!_ means "A strange man has come!"
_Dysgrammatism_ (Kussmaul) _and Agrammatism_ (Steinthal).--Children can _not yet_ put words into correct grammatical form, decline, or conjugate. They like to use the indefinite noun-substantive and the infinitive, likewise to some extent the past participle. They prefer the weak inflection, ignore and confound the articles, conjunctions, auxiliaries, prepositions, and p.r.o.nouns. In place of "I" they say their own names, also _tint_ (for "Kind"--child or "baby"). Instead of "Du, er, Sie" (thou, he, you), they use proper names, or man, papa, mamma.
Sometimes, too, the adjectives are placed after the nouns, and the meaning of words is indicated by their position with reference to others, by the intonation, by looks and gestures. Agrammatism in child-language always appears in company with acataphasia, often also in insane persons. When the imbecile Tony says, "Tony flowers taken, attendant come, Tony whipped" (Tony Blumen genommen, Warterin gekommen, Tony gehaut), she speaks exactly like a child (Kussmaul), without articles, p.r.o.nouns, or auxiliary verbs, and, like the child, uses the weak inflection. The connection _m_ of the word-image-center W with the diction-center D, i. e., of the word-memory with grammar, and the centers themselves, are as yet very imperfectly developed, unused.