[Illustration: Median Section of _Mouth_, _Nose_, _Pharynx_, and _Larynx_:—_a_, septum of nose; below it, section of hard palate; _b_, tongue; _c_, section of velum pendulum palati; _d_, _d_, lips; _u_, uvula; _r_, anterior arch or pillar of fauces; _i_, posterior arch; _t_, tonsil; _p_, pharynx; _h_, hyoid bone; _k_, thyroid cartilage; _n_, crycoid cartilage; _s_, epiglottis; _v_, glottis; 1, posterior opening of nares; 3, isthmus faucium; 4, superior opening of larynx; 5, passage into œsophagus; 6, mouth of right Eustachian tube.] _ORGANS WHICH REINFORCE VOICE._ The organs that reinforce voice are its resonant chambers, viz.:— Nares, Mouth, Pharynx, Trachea. Resonance means resounding or sounding again, and is caused by means of the air conveying the vibrations of one substance to another substance. This is familiarly illustrated in the echo. There are two classes of resonant chambers; one class is comparatively fixed, and consists of the nares and trachea; the other class may, for convenience, be termed the transient forms of resonance. [2]A transient resonant chamber is one that is formed on the instant for a particular purpose, and may be broken as quickly. Elements of speech are formed by producing a succession of definitely formed but transient molds of resonance. The pharynx is for the purpose of reinforcing the tone, giving it projection and some assistance in proper direction. All the other transient resonant molds are for the purpose of producing elements of speech. ----- [2] See Tyndall on sound, page 227. NARES (Nasal cavities). The nares are the cavities in the head extending through the nose to the pharynx. The walls of the nares are smooth, and, with their turbinated bones, suggest the inside of a sea-shell. PHARYNX. The pharynx is a membranous sac. It has seven openings, the two posterior nares, the two Eustachian tubes, the larynx, the œsophagus, and the isthmus faucium, which is the opening into the mouth. [Illustration: =LARYNX, TRACHEA, AND BRONCHI.=] TRACHEA. The trachea, or windpipe, is a cylindrical tube extending from the lower part of the larynx to where it divides into the bronchi. The interior surface is firm and beautiful. _ORGANS WHICH GIVE RESONANT FORMS TO VOICE._ Lips, Upper gum, Hard palate, Soft palate, Tongue, Nares. Although the quality of the voice produced by the vocal cords of the human being cannot be distinguished from that produced by the vocal cords of the lower animals the organs which resound it give it a distinct quality.