[Illustration: e, e, the vocal cords; d, the epiglottis.]
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.
[Illustration: The Lungs, showing the Larynx. A, the windpipe; B, the bronchial tubes.]
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 sophagus. 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.
[Illustration: Bronchial Tubes, with clusters of cells.]