595. The larynx is much more developed and prominent in man than in woman. In the former, the anterior angle of the thyroid cartilage is acute, while in the latter it is rounded, and the central slope of the superior border of the same cartilage is less deep, and the epiglottis smaller and less prominent, than in man.

596. The difference in the formation of the larynx in infancy is less striking; but at a later period, it is more developed in the male than in the female. It is very remarkable that this increase is not progressive, like that of other organs, but, on the contrary, develops itself at once at the period of puberty.

PHYSIOLOGY OF THE VOCAL ORGANS.

597. In the formation, of the voice, each part already described performs an important office. The cricoid and thyroid cartilages give form and stability to the larynx; the arytenoid cartilages, by their movement, vary the width of the glottis. The epiglottis is flexible and elastic. When it is erect, the chink of the glottis is open, as in inspiration; when depressed, as in swallowing food and drink, it covers and closes this aperture. It prevents the introduction of articles of food into the trachea, and probably modifies sound as it issues from the glottis.

598. The muscles of the neck elevate and depress the larynx; the muscles of the larynx increase or diminish the width of the glottis; at the same time, the vocal cords are

595. What difference between the formation of the larynx of the female and that of the male? 596. Does this difference exist in childhood? Is its development progressive? 597-600. Give the physiology of the vocal organs. 597. Which cartilages give stability and form to the larynx? Which vary the width of the glottis? What is the function of the epiglottis? 598. What effect have the muscles of the neck upon the larynx? The use of the muscles of the larynx ?

relaxed or tightened, while the muscles of the face open and close the mouth.

599. The elasticity of the ribs and the contraction of the abdominal muscles diminish the cavity of the chest, and the air, in consequence, is pressed from the air-cells into the bronchial tubes and trachea. It then rushes by the vocal cords, and causes a peculiar vibration, which produces sound. Observations. 1st. Experiments have satisfactorily shown that the vocal cords are the principal agents in the formation of the voice. The tongue, which many have supposed to be the most important organ in speaking, is not essential to sound. In several instances it has been removed, and the persons thus mutilated could speak with fluency.

2d. When the vocal cords are ulcerated, or inflamed, however slightly, as in sore throat produced by a cold, the voice will be changed. The loss of speech among public speakers is generally produced by a relaxation of the vocal ligaments. Hence, bronchitis is a misnomer for this affection.

600. Sound is varied by the velocity of the expelled current of air, and the tension of the vocal ligaments. The size of the larynx, the volume and health of the lungs, the condition of the fauces and nasal passages, the elevation and depression of the chin, the development and freedom of action of the muscles which are attached to the larynx, the opening of the mouth, the state of the mind, and general health of the system, influence the modulations of sound.

What effect has the combined action of these muscles? 599. How is sound produced? What have experiments shown? What effect has dis ease of the vocal ligaments upon the voice? 600. How is sound varied? Mention other conditions that contribute to the modulation of sound.

595. The larynx is much more developed and prominent in man than in woman. In the former, the anterior angle of the thyroid cartilage is acute, while in the latter it is rounded, and the central slope of the superior border of the same cartilage is less deep, and the epiglottis smaller and less prominent, than in man..

596. The difference in the formation of the larynx in infancy is less striking; but at a later period, it is more developed in the male than in the female. It is very remarkable that this increase is not progressive, like that of other organs, but, on the contrary, develops itself at once at the period of puberty.

PHYSIOLOGY OF THE VOCAL ORGANS.

597. In the formation, of the voice, each part already described performs an important office. The cricoid and thyroid cartilages give form and stability to the larynx; the arytenoid cartilages, by their movement, vary the width of the glottis. The epiglottis is flexible and elastic. When it is erect, the chink of the glottis is open, as in inspiration; when depressed, as in swallowing food and drink, it covers and closes this aperture. It prevents the introduction of articles of food into the trachea, and probably modifies sound as it issues from the glottis.

598. The muscles of the neck elevate and depress the larynx; the muscles of the larynx increase or diminish the width of the glottis; at the same time, the vocal cords are

595. What difference between the formation of the larynx of the female and that of the male? 596. Does this difference exist in childhood? Is its development progressive? 597–600. Give the physiology of the vocal organs. 597. Which cartilages give stability and form to the larynx? Which vary the width of the glottis? What is the function of the epiglottis? 598. What effect have the muscles of the neck upon the larynx? The use of the muscles of the larynx?

relaxed or tightened, while the muscles of the face open and close the mouth.

599. The elasticity of the ribs and the contraction of the abdominal muscles diminish the cavity of the chest, and the air, in consequence, is pressed from the air-cells into the bronchial tubes and trachea. It then rushes by the vocal cords, and causes a peculiar vibration, which produces sound.

Observations. 1st. Experiments have satisfactorily shown that the vocal cords are the principal agents in the formation of the voice. The tongue, which many have supposed to be the most important organ in speaking, is not essential to sound. In several instances it has been removed, and the persons thus mutilated could speak with fluency.

2d. When the vocal cords are ulcerated, or inflamed, however slightly, as in sore throat produced by a cold, the voice will be changed. The loss of speech among public speakers is generally produced by a relaxation of the vocal ligaments. Hence, bronchitis is a misnomer for this affection.

600. Sound is varied by the velocity of the expelled current of air, and the tension of the vocal ligaments. The size of the larynx, the volume and health of the lungs, the condition of the fauces and nasal passages, the elevation and depression of the chin, the development and freedom of action of the muscles which are attached to the larynx, the opening of the mouth, the state of the mind, and general health of the system, influence the modulations of sound.

What effect has the combined action of these muscles? 599. How is sound produced? What have experiments shown? What effect has dis ease of the vocal ligaments upon the voice? 600. How is sound varied? Mention other conditions that contribute to the modulation of sound.

CHAPTER XXX.

HYGIENE OF THE VOCAL ORGANS.

601. The voice can be changed and modified by habit. Sailors, smiths, and others, who are engaged in noisy occupations, exert their vocal organs more strongly than those of more quiet pursuits. This not only affects the structure of the vocal organs, but varies the intonation of the voice.

602. The voice is strong in proportion to the development of the larynx, and the capacity of the chest. Singing and reading aloud improve and strengthen the vocal organs, and give a healthy expansion to the chest. The enunciation of the elementary sounds of the English language, aids in developing the vocal organs, as well as preventing disease of the throat and lungs. This exercise also conduces to the acquisition of musical sounds.

603. The attitude affects the modulation of the voice. When an individual stands erect, the movements of the whole respiratory apparatus are most free and effective. The larynx is brought forward by the erect position of the head and the elevation of the chin. The muscles of the arytenoid cartilages are then brought to a proper relation for action, by which a tension of the vocal cords is produced, that favors clear and harmonious enunciation.

Experiment. Read with the head bowed forward and the chin depressed; then read with the head erect and the chin elevated, and the difference in the movement of the vocal

601-616. Give the hygiene of the vocal organs. 602. How may the voice be strengthened? 603. What effect has the erect attitude upon the modulations of the voice? Give the experiment.