STAMMER. The terms stammer and stutter are synonymously adopted to denote the involuntary interruption of utterance arising from difficulty and often total inability to pronounce certain syllables, the speech apparatus being frequently affected with spasm in the effort to speak.
In some stammerers the spasm consists of involuntary movements similar to chorea (St. Vitus's dance), which occasionally affects other than the speech muscles. Stammer with this spasm distorts the utterance by an involuntary repetition of some part of the syllable, as ge-ge-ge-good de-de-de-day. The repetitions may or may not be vocal. In other stammerers the spasm consists of Involuntary immobility, similar to tetanus (lock-jaw), commonly of the form termed t,-ismus, tn which the mouth is closed, and the jaw cannot move to open it ; and sometimes of the form termed antitrismus, in which the mouth is open, and the jaw Is equally incapable of moving to shut it. Stammer with this spasm distorts the utterance by an involuntary extension of some part of the syllable, as 1—augh, where the 1 is rnnch pro longed.
In the looseness of language resulting from inexact knowledge, all kinds of difficult and defective utterance are misnamed stammer; as the difficult utterance of the intoxicated, the faltering utterance of the paralytic, the imperfect utterance of deep emotion, as of fear, the defective utterance of malformed organs of speech, and the hesita tion in discourse when the suitable word fails to present itself to a speaker's mind. Such affections of the utterance, however, are distinct from stammer, for 1. The etaminerer's inability to pronounce words remains during health, soberness, calmness of mind, and also when the appropriate words occur to him.
2. The stammerer feels his difficulty of utterance essentially to consist in a refusal of some part of the speech apparatus to obey his will.
3. The stammerers utmost efforts to force out any difficult word commonly excite spasm, and increase it If it previously existed.
4. The stammerer's inability to speak is intermittent : the same syllable is not always equally difficult to utter, and is sometimes uttered with ease.
Those circumstances will distinguish stammer from the misnamed stammer of paralysis, intoxication, &c.
Now, to understand the nature of stammering, it is necessary to know the audibility and mechanism of utterance, which may be thus briefly described : The voice is produced in the larynx, whence It issues into the pharynx. The pharynx opens into the nose and into the mouth ; and by means of a curtain valve, named the return pendulum palati, we can direct the issue of breath through the mouth or the nose, or through both mouth and nose at once. The voice is produced in the larynx, en audible sound, which may possess the distinctions of song-notea (musical sounds), as those of pitch, loudness, and quality; or it may possess the peculiar conditions of those distinctions which constitute speech notes. In the pharynx and mouth the volume of svoice is magnified, and its quality is modified.
Observation and experiment concur to prove that the production of voice is an acoustic phenomenon depending on mechanical principles similar to those which regulate the production of sound from an inanimate instrument ; for it is now agreed that the upward current of air passing through the larynx produces an effect on the vocal ligaments precisely similar to what it would if the larynx were an inanimate mechanism. The voluntary power over the larynx adjusts it to be acted on by the current of air, and thus the voice is to be regarded partly as a mechanical and partly as a physiological result.
Observation and experiment concur to prove that the modification of voice into speech is also an acoustic phenomenon depending on principles similar to those which regulate the modification of sound by an inanimate instrument ; for it is now agreed that the modification of voice into speech in passing through the variable cavity of the pha rynx, mouth, and nose, produces an effect precisely similar to what would be produced if the variable cavity were an inanimate me chanism.