Popular Science Monthly/Volume 24/February 1884/How We Sneeze, Laugh, Stammer, and Sigh
|HOW WE SNEEZE, LAUGH, STAMMER, AND SIGH.|
By FREDERIC A. FERNALD.
THE nose is an organ in more senses than one. From its resonant pipes proceed the sonorous tones which tell of blissful slumber, and the convulsive snort, varying from the mere "cat-sneeze" to the tremendous "Horatio," that has less definite meaning; while the Frenchman and the typical New-Englander (who is nearly as rare as the aborigine in New England, by-the-way) give it an important share in the production of speech. To give some physiological explanation of these and other involuntary actions of the respiratory mechanism is the object of the present article.
Snoring is produced in sleep by the passage of the breath through the pharynx when the tongue and soft palate are in certain positions. The soft palate must have fallen back in such a manner as to nearly or quite close the entrance to the nasal cavity from the throat, and the tongue must also be thrown back so far as to leave only a narrow opening between it and the soft palate. It is by the air being forced either inward or outward through this opening that the noise is produced. A snore results also when, with a closed mouth, the air is forced between the soft palate and the back wall of the pharynx into the nasal cavity. With deep breathing, perhaps accompanied by a variation in the position of the soft palate, a rattling noise may be heard in addition to the snoring, which is due to a vibration of the soft palate. Hence it is evident how flinging a pillow at a snorer, or poking him in the ribs, will often cause him to be silent even when the disciplinary measure does not awaken him, for a change of position that lets the tongue and soft palate fall a little forward secures a free passage for the air.
Grunting is a noise which is produced when, after the larynx has been perfectly closed, whether spasmodically or as a voluntary action with the object of holding the breath, the current of air thus interrupted is suddenly resumed. In the grunt we must distinguish two elements: the first is a clicking sound, and the other an explosive sound or slight report. The click is the noise produced by the meeting of air in the space left vacant when two moistened bodies are suddenly separated. It forms, however, but a very small part of the noise of grunting, and can scarcely be experimentally demonstrated. The "report" is the well-known phenomenon connected with the sudden expansion of a body of compressed air.
"Talking through the nose" when a person has a cold is in reality talking with the nose so stopped that less rather than more than the usual quantity of vibrating air can pass through the nasal cavity. In producing certain articulate sounds—those which occur in English are represented by m, n, and ng—all the vocal air escapes from the pharynx by the nose. The nasal air-passage has the general form of a resonator, and there can be no doubt but that it has a corresponding influence, and that the sounds produced by the air passing through it are strengthened by its resonance. The larger the nasal cavity the more powerful the resonance, and consequently the re-enforcement experienced by the tone. Sounds uttered with the nasal resonance, particularly the nasal vowels, are fuller and more ample than the same sounds when strengthened by the resonance of the cavity of the mouth, and it is for this reason that third-rate tragic actors like to give a nasal resonance to all the vowels in the pathetic speeches of their heroic parts. The resonance of the nasal cavity plays a part also in the formation of non-nasal articulate sounds; then, however, appearing only as a re-enforcement of the resonance of the cavity of the mouth. The directly excited nasal resonance sometimes plays an immediate part in the formation of all articulate sounds, producing the nasal "twang." But the general conception of this mode of speaking is by no means scientifically correct, every species of pronunciation in which the nasal element asserts itself with undue prominence being called "talking through the nose." It may, however, arise from two unlike causes: firstly, from a stoppage of the nasal cavity; or, secondly, from incomplete closure of the posterior entrance to this cavity. If the nasal cavity is obstructed, as when a child's nose is pinched and he is told to say "pudding," an accumulation of air forms in the back of the mouth, being unable to escape through the nose, and in the end is obliged to find exit through the mouth. The resonance is also altered, and the nasal sounds are, therefore, formed imperfectly and falsely. The same disturbance is produced by the partial obstruction of the nasal cavity which is experienced from the swollen condition of the mucous membrane, and from its increased secretion, during a "cold in the head."
A nasal twang from improper escape of air through the nasal cavity may be due to a cleft palate, or to some less grave defect which prevents insufficient contact between the soft palate and the back wall of the pharynx. Various other noises emanate from the mouth and nose, accompanying certain unusual and mainly involuntary forms of respiration. These are classified by Yon Meyer, from whose "Organs of Speech," in the "International Scientific Series," most of the material for this article has been obtained, as disturbances of inspiration, to which class belong hiccough, gaping, and stammering, and disturbances of expiration, under which he enumerates sneezing, coughing, laughing, and sighing.
Hiccough is the simplest of the former class, and is merely a violent inspiration caused by a convulsive contraction of the diaphragm. The ensuing expiration then takes place quietly. The air inhaled may enter principally either through the mouth or the nose, or through both equally, and in each case the accompanying noise is different. A contraction of the glottis may also take place at the same time, and in this case the entering stream of air creates, in passing between the vocal chords, a sharp, clear tone. During an attack, one inspiration in about four or five is convulsive. Hiccough arises from over-irritation of the nerves of the diaphragm, the cause of which we know to be either psychical conditions or overfilling of the stomach. When the stomach is overladen with food or with effervescing or alcoholic drinks, it resists to a greater or less extent the fall of the diaphragm; the contractions of the diaphragm necessarily become more labored, and occasionally, like other over-irritated muscles, assume a convulsive character. Frequently, however, the hiccough appears as a sign of the general over-irritation of the nervous system in hysteria, and, probably from the same reason, it may not uncommonly be observed in otherwise healthy young persons, particularly children. The above explanation of hiccough as a convulsive contraction of the diaphragm is further confirmed by the manner in which it may be stopped. It is, namely, only necessary to allow an exceedingly protracted and, at the end, forcible expiration to follow a long and quiet inspiration. The slow inspiration, especially when it is chiefly performed by the wall of the chest, prevents the phrenic nerve from being too powerfully irritated, while the long expiration gives this nerve time to recover from its over-irritation. A remedy which the writer has tested many times without a failure can always be used upon a person who has "the hiccoughs" by some one else, and generally by the sufferer himself. You say to your friend something like this: "See how close together you can hold the tips of your forefingers without their touching. No, keep your elbows out free from your sides. You can get your fingers closer than that. They are touching now. There, now hold them so. Steady." By this time you can generally ask, "Now, why don't you hiccough?" The involuntary tendency to breathe slowly and steadily when the attention is fixed on performing a delicate manipulation is here what counteracts the convulsive action of the diaphragm.
Gaping is also a convulsive form of inspiration, which, however, is not so short and violent as the hiccough. In gaping, moreover, those muscles which raise the walls of the chest are at once brought into prominent action; while, further, a rapid contraction of the diaphragm is necessary before the climax can be reached, after which a somewhat rapid fall of the thorax produces a quick expiration. The important part which is played by the rise of the chest is particularly shown by the fact that in very violent gaping the head is thrown backward, and the shoulders raised, in addition to which even the arms are sometimes stretched upward. During the gaping inspiratory process the mouth is opened spasmodically, and at the same time the soft palate is spasmodically raised, closing the air-passage of the nose. The whole phenomenon, including the sense of satisfaction after the inspiration, seems an indication of a strong desire for air, and the existence of this desire under those circumstances in which gaping is generally observed—sleepiness, for instance, or weariness—is readily explainable. Such circumstances are accompanied by a general inactivity of the nervous system, from which results a weak respiratory action, insufficient for the body when awake.
Stammering results from efforts to talk while a similar action to that which produces hiccough is going on. The difference is that, in stammering, the contractile spasm of the diaphragm is longer. During its continuance no expiration can take place, and, as speech depends upon the existence of an issuing stream of air, it is impossible for a person while suffering such a spasm to produce any sound. Ineffectual and therefore exaggerated efforts to create sound with the organs of the mouth and throat give rise to distressed grimaces, and this distressed expression must necessarily be augmented by the fact that, by so long delaying expiration, a want of breath is felt and the circulation of the blood interrupted. "When at length the spasm ceases, and is followed by a quick expiration, the natural condition is restored till again destroyed by a fresh spasm. But there may be no attempt to speak, and yet the cause of the phenomenon (the spasm in the diaphragm) may be experienced; in this case it will not cause stammering, and may be quite imperceptible to the observer. If, now, as appears from the above, stammering is only an occasionally observed symptom of a contractile spasm in the diaphragm, it must be clear that all attempts to cure stammering by exercising the organs of the mouth and throat must be unsuccessful, and that this defect can be efficiently treated only by following rules already given for the treatment of hiccough. A quiet, unhurried inspiration must be followed by an expiration as slow and long as possible, the issuing stream either being employed in speech or not. With this treatment the motor nerves of the diaphragm can most effectually recover from their state of over-irritation, and return to their normal condition. We must, however, be careful not to fall into the common error of confounding stuttering with stammering. In stuttering the process of breathing is quite normal, and the defective speech arises only from inaptitude in the formation of sound; this defect of speech is, therefore, peculiar to children, idiots, and persons suffering from apoplexy.
Sighing, which is classed by Von Meyer as an unusual form of expiration, is better regarded as including the preceding inspiration also. A sigh is in fact a long breath, and, like a gape, is an involuntary spurt made to catch up with the demand for air. This is true even when it arises from depressing emotion. The expiration is often the more prominent part of the action, the rapidity with which the air flows out being due to a sudden cessation of the activity of the expiratory muscles, which commonly regulate, by retarding, the issuing stream of air. In sobbing, air is obtained by short, abrupt inspirations, and the tears which overflow into the nasal cavity assist in causing this air to produce sound.
Sneezing is the simplest of the purely expiratory noises. Just as the hiccough depends upon a single violent spasm during inspiration, so the sneeze is due to a single violent spasm during expiration, generally of the abdominal muscles, but, when very violent, of the other expiratory muscles also. It is a reflex action which occurs after an irritation of the mucous membrane lining the air-passages of the nose, and also after irritation of the optic nerve by a bright light. A few slight contractions of the abdominal muscles are at first suppressed by some short inspirations rapidly following each other without any intervening expiration; then follows a vigorous contraction of the abdominal muscles, by means of which the stream of air is violently driven out through the mouth and nose. In its passage through the nose, the air produces a well-known noise, which may, however, be connected with a sound produced in the vocal chords. We recognize the same peculiarity, though the action is voluntarily performed, in blowing the nose. Sneezing is not an observer of times and seasons, and often seems to choose the most inopportune moment for exhibiting its power. In such a case the impending catastrophe may be averted by pressing firmly upon some branch of the fifth nerve, say in the upper lip close under the nose.
Coughing and laughing are also due to a spasmodic contraction of the expiratory muscles. These acts differ from sneezing only in this respect, that, while in the latter expiration is accomplished by a single violent action, it is here characterized by a number of separate impulses of the expiratory muscles with small intervening pauses. In long-continued coughing or laughing, short inspirations, which, on account of their shortness and violence, often approach the verge of hiccoughing, are taken between the separate expirations, and, indeed, laughing after a full meal frequently leads to a fit of hiccoughs. Coughing most closely resembles sneezing, not only as regards its origin, but also as regards its execution. This is a reflex action which follows an irritation of the air-passages, particularly of the windpipe and the larynx, but also of the pharynx and the nasal cavity. Stimulation of other nerves, as those of the skin by a draught of cold air, may also produce coughing. The expiratory impulses induced may attain great violence, so as in this respect to resemble the single impulse of sneezing. While, however, in sneezing, the stream of air escapes, as a rule, through the nose, in coughing it escapes through the cavity of the mouth, which is shut off by the raised soft palate from the nasal cavity, and enlarged by dropping the lower jaw, and by the depression of the floor of the cavity, the tongue at the same time being pushed forward. The closed glottis holds this air back for an instant against the pressure of the abdominal muscles, and then suddenly opens part way, letting it escape with an explosive noise, generally accompanied by a sound, shrill or deep as the case may be, produced by the vocal chords. Performed voluntarily, and with less violence, coughing assumes the form known to us as "clearing the throat." In laughing, the separate expiratory impulses are not so violent, and the stream of air passes through the fairly open mouth, or, when the mouth is shut, through the nose. It is accompanied by contractions of the muscles of the face, and is mainly involuntary, being generally caused by an impression produced upon the higher parts of the brain. Violent laughing may be caused by tickling some parts of the body. Characteristic sounds are produced in the same way as already described in coughing, and in both, when long continued, the air which from time to time is quickly inspired may produce a clear, shrill note in passing through the glottis.