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. [Illustration: _Passage to the Œsophagus and Windpipe._ c, _the tongue;_ d, _the soft palate, ending in_ g, _the uvula;_ h, _the epiglottis;_ i, _the glottis;_ I, _the œsophagus;_ f, _the pharynx._] 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. [Illustration: e, e, _the vocal cords;_ d, _the epiglottis._]