The discovery of the laryngoscope by Garcia enabled him by its means to see the vocal cords in action and how the reed portion of the vocal instrument works (vide fig. 9 and description).  The chink of the glottis or the opening between the vocal cords as seen in the mirror of the laryngoscope varies in size.  The vocal cords or ligaments appear dead white and contrast with the surrounding pink mucous membrane covering the remaining structures of the larynx.  Fig. 10 shows the appearance of the glottis in respiration and vocalisation.  The vocal cords of a man are about seven-twelfths of an inch in length, and those of a boy (before the voice breaks) or of a woman are about five-twelfths of an inch; and there is a corresponding difference in size of the voice-box or larynx.  This difference in length of the vocal cords accounts for the difference in the pitch of the speaking voice and the register of the singing voice of the two sexes.  We should also expect a constant difference in the length of the cords of a tenor and a bass in the male, and of the contralto and soprano in the female, but such is not the case.  It is not possible to determine by laryngoscopic examination what is the natural register of an individual’s voice.  The vocal cords may be as long in the tenor as in the bass; this shows what an important part the resonator plays in the timbre or quality of the voice.  Still, it is generally speaking true, that a small larynx is more often associated with a higher pitch of voice than a large larynx.

[Illustration:  Fig. 10]

[Description:  Fig. 10.—­Diagram (modified from Aikin) illustrating the condition of the vocal cords in respiration, whispering, and phonation. (1) Ordinary breathing; the cords are separated and the windpipe can be seen. (2) Deep inspiration; the cords are widely separated and a greater extent of the windpipe is visible. (3) During the whisper the vocal cords are separated, leaving free vent for air through the glottis; consequently there is no vibration and no sound produced by the cords. (4) The soft vocal note, or aspirate, shows that the chink of the glottis is not completely closed, and especially the rima respiratoria (the space between the vocal processes of the pyramidal cartilages.) (5) Strong vocal note, produced in singing notes of the lower register. (6) Strong vocal note, produced in singing notes of the higher register.]

Musical notes are comprised between 27 and 4000 vibrations per second.  The extent and limit of the voice may be given as between C 65 vibrations per second and f’’’ 1417 vibrations per second, but this is most exceptional, it is seldom above c’’’ 1044 per second.  The compass of a well-developed singer is about two to two and a half octaves.  The normal pitch, usually called the “diapason normal,” is that of a tuning-fork giving 433 vibrations per second.  Now what does the laryngoscope teach regarding the change occurring in the vocal cords during the singing of the two to two and a half