Part 14

40. Why should we take special pains to avoid clothing that is colored by poisonous dyestuffs? (See p. 296.)

41. What general principles should guide us as to the length and frequency of baths In salt or fresh water?

42. What is the beneficial effect of exercise upon the functions of the skin?

43. How can we best show our admiration and respect for the human body?

44. Why is the scar of a severe wound upon a negro sometimes white?

IV.

RESPIRATION AND THE VOICE.

"The smooth soft air with pulse-like waves Flows murmuring through its hidden caves, Whose streams of brightening purple rush, Fired with a new and livelier blush; While all their burden of decay The ebbing current steals away."

ANALYSIS OF RESPIRATION AND THE VOICE.

| 1. The Larnyx. | 2. The Vocal Cords. | 1. ORGANS OF VOICE.....| 3. Different Tones of Voice. | | 4. Speech. | |5. Formation of Vocal Sounds. | | | 1. The Trachea. | | 2. The Bronchial Tubes. | 2. ORGANS OF RESPIRA- | 3. The Cells. | TION.........| 4. The Lung Wrapping. | |5. The Cilia. | | | 1. Inspiration. | 3. HOW WE BREATHE......|2. Expiration. | | | 1. Sighing. | | 2. Coughing. | | 3. Sneezing. | 4. MODIFICATIONS OF | 4. Snoring. | THE BREATH.......| 5. Laughing, and Crying. | | 6. Hiccough. | |7. Yawning. | | 5. CAPACITY OF THE LUNGS. | | | 1. The Need of Air. | | 2. Action of Air in the Lungs. | | 3. Tests of the Breath. | | 4. Analysis of Expired Air. | | 5. Effect of Rebreathed Air. | | | 6. HYGIENE.............| | a. The Sources of | | | Impurity. | | | b. The Sick Room. | | 6. Concerning | c. The Sitting Room. | | the Need of | d. The Bedroom. | | Ventilation.| e. The Church. | | f. The Schoolroom. | | g. How we should | | Ventilate. | | 7. THE WONDERS OF RESPIRATION. | | | 1. Constriction of the Lungs. | | 2. Bronchitis. | | 3. Pleurisy. | | 4. Pneumonia. |8. DISEASES............| 5. Consumption | 6. Asphyxia. | 7. Diptheria. | 8. Croup. |9. Stammering.

RESPIRATION AND THE VOICE.

The Organs of Respiration and the Voice are the larynx, the trachea, and the lungs.

DESCRIPTION OF THE ORGANS OF THE VOICE.--l. The Larynx.--In the neck, is a prominence sometimes called Adam's apple. It is the front of the larynx. This is a small triangular, cartilaginous box, placed just below the root of the tongue, and at the top of the windpipe. The opening into it from the throat is called the glottis; and the cover, the epiglottis (epi, upon; glotta, the tongue). The latter is a spoon-shaped lid, which opens when we breathe, but, by a nice arrangement, shuts when we try to swallow, and so lets our food slip over it into the œsophagus (e-sof'-a-gus), the tube leading from the pharynx to the stomach (Fig. 27).

If we laugh or talk when we swallow, our food is apt to "go the wrong way," i. e., little particles pass into the larynx, and the tickling sensation which they produce forces us to cough in order to expel the intruders.

2. The Vocal Cords.--On each side of the glottis are the so- called vocal cords. They are not really cords, but merely elastic membranes projecting from the sides of the box across the opening. [Footnote: The cartilages and vocal cords may be readily seen in the larynx of an ox or sheep. If the flesh be cut off, the cartilages will dry, and will keep for years.] When not in use, they spread apart and leave a V-shaped orifice (Fig. 28), through which the air passes to and from the lungs. If the cords are tightened, the edges approach sometimes within 1/100 of an inch of each other, and, being thrown into vibration, cause corresponding vibrations in the current of air. Thus sound is produced in the same manner as by the vibrations of the tongues of an accordion, or the strings of a violin, only in this case the strings are scarcely an inch long.

FIG. 27.

DIFFERENT TONES OF THE VOICE.--The higher tones of the voice are produced when the cords are short, tight, and closely in contact; the lower, by the opposite conditions. Loudness is regulated by the quantity of air and force of expulsion. A falsetto voice is thought to be the result of a peculiarity in the pharynx (Fig. 27) at the back part of the nose; it is more probably produced by some muscular maneuver not yet fully understood. When boys are about fourteen years of age, the larynx enlarges, and the cords grow proportionately longer and coarser; hence, the voice becomes deeper, or, as we say, "changes." The peculiar harshness of the voice at this time seems to be due to a congestion of the mucous membrane of the cords. The change may occur very suddenly, the voice breaking in a single night.

FIG. 28.

Speech is voice modulated by the lips, tongue, [Footnote: The tongue is styled the "unruly member," and held responsible for all the tattling of the world; but when the tongue is removed, the adjacent organs in some way largely supply the deficiency, so that speech is still possible. Huxley describes the conversation of a man who had two and one half inches of his tongue preserved in spirits, and yet could converse intelligibly. Only the two letters t and d were beyond his power; the articulation of these involves the employment of the tip of the tongue; hence, "tin" he converted into "fin," and "dog" into "thog."] palate, and teeth. [Footnote: An artificial larynx may be made by using elastic bands to represent the vocal cords, and by placing above them chambers which by their resonance will produce the same effect as the cavities lying above the larynx. An artificial speaking machine was constructed by Kempelen, which could pronounce such sentences as, "I love you with all my heart," in different languages, by simply touching the proper keys.] Speech and voice are commonly associated, but speech may exist without the voice, for when we whisper we articulate the words, although there is no vocalization, i. e., no action of the larynx. [Footnote: We can observe this by placing the hand on the throat, and noticing the absence of vibrations when we whisper, and their presence when we talk. The difference between vocalization and non-vocalization is seen in a sigh and a groan, the latter being the former vocalized. Whistling is a pure mouth sound, and does not depend on the voice. Laughter is vocal, being the aspirated vowels, a, e, or o, convulsively repeated.] (See p. 297.)

FIG. 29.

FORMATION OF VOCAL SOUNDS.--The method of modulating voice into speech may be seen by producing the pure vowel sounds a, e, etc., from one expiration, the mouth being kept open while the form of the aperture is changed for each vowel by the tongue and the lips. H is only an explosion, or forcible throwing of a vowel sound from the mouth. [Footnote: When, in sounding a vowel, the sound coincides with a sudden change in the position of the vocal cords from one of divergence to one of approximation, the vowel is pronounced with the spiritus asper. When the vocal cords are brought together before the blast of air begins, the vowel is pronounced with the spiritus lenis.--FOSTER.]

The consonants, or short sounds, may also be made without interrupting the current of air, by various modifications of the vocal organs. In sounding singly any one of the letters, we can detect its peculiar requirements. Thus m and n can be made only by blocking the air in the mouth and sending it through the nose; l lets the air escape at the sides of the tongue; r needs a vibratory movement of the tongue; b and p stop the breath at the lips; k and g (hard), at the back of the palate. Consonants like b and d are abrupt, or, like l and s, continuous. Those made by the lips are termed labials; those by pressing the tongue against the teeth, dentals; those by the tongue, linguals.

The child gains speech slowly, first learning to pronounce the vowel a, the consonants b, m, and p, and then their unions --ba, ma, pa.

DESCRIPTION OF THE ORGANS OF RESPIRATION.--Beneath the larynx is the windpipe, or trachea (see Fig. 29), so called because of its roughness. It is strengthened by C-shaped cartilages with the openings behind, where they are attached to the œsophagus. At the lower end, the trachea divides into two branches, called the right and left bronchi. These subdivide in the small bronchial tubes, which ramify through the lungs like the branches of a tree, the tiny twigs of which at last end in clusters of cells so small that there are six hundred million in all. This cellular structure renders the lungs exceedingly soft, elastic, and sponge-like. [Footnote: The lungs of slaughtered animals are vulgarly called "lights," probably on account of their lightness. They are similar in structure to those of man. They will float on water, and if a small piece be forcibly squeezed between the fingers (notice the creaking sound it gives), it will retain sufficient air to make it buoyant.]

FIG. 30.

The stiff, cartilaginous rings, so noticeable in the rough surface of the trachea and the bronchi, disappear as we reach the smaller bronchial tubes, so that while the former are kept constantly open for the free admission of air, the latter are provided with elastic fibers by which they may be almost closed.

WRAPPING OF THE LUNGS.--The lungs are invested with a double covering--the pleura--one layer being attached to the lungs and the other to the walls of the chest. It secretes a fluid which lubricates it, so that the layers glide upon each other with perfect ease. [Footnote: These pleural sacs are distinct and closed; hence, when the ribs are raised, a partial vacuum being formed in the sacs, air rushes in, and distends the pulmonary lobules.] The lungs are lined with mucous membrane, exceedingly delicate and sensitive to the presence of anything except pure air. We have all noticed this when we have breathed any thing offensive.

FIG. 31.