octaves?  If the vocal cords are observed by means of the laryngoscope during phonation, no change is seen, owing to the rapidity of the vibrations, although a scale of an octave may be sung; in the lower notes, however, the vocal cords are seen not so closely approximated as in the very high notes.  This may account for the difficulty experienced in singing high notes piano.  Sir Felix Semon in a Friday evening lecture at the Royal Institution showed some remarkable photographs, by Dr. French, of the larynx of two great singers, a contralto and a high soprano, during vocalisation, which exhibit changes in the length of the vocal cords and in the size of the slit between them.  Moreover, the photographs show that the vocal cords at the break from the lower to the upper register exhibit characteristic changes.

[Illustration:  Fig. 11]

[Description:  Fig. 11.—­Drawings after Dr. French’s photographs in Sir Felix Semon’s lecture on the Voice, (1) Appearance of vocal cords of contralto singer when singing F# to D; it will be observed that the cords increase in length with the rise of the pitch, presumably the whole cord is vibrating, including the inner strand of the vocal muscle.  At the break from D to E (3 and 4) the cords suddenly become shorter and thicker; presumably the inner portion of the vocal muscle (thyro-arytenoid) is contracting strongly, permitting only the edge of the cord to vibrate.  For the next octave the cords are stretched longer and longer; this may be explained by the increasing force of contraction of the tensor muscle stretching the cords and the contained muscle, which is also contracted.]

When we desire to produce a particular vocal sound, a mental perception of the sound, which is almost instinctive in a person with a musical ear, awakens by association motor centres in the brain that preside over the innervation currents necessary for the approximation and minute alterations in the tensions of the vocal cords requisite for the production of a particular note.  We are not conscious of any kinaesthetic (sense of movement) guiding sensations from the laryngeal muscles, but we are of the muscles of the tongue, lips, and jaw in the production of articulate sounds.  It is remarkable that there are hardly any sensory nerve endings in the vocal cords and muscles of the larynx, consequently it is not surprising to find that the ear is the guiding sense for correct modulation of the loudness and pitch of the speaking as well as the singing voice.  In reading music, visual symbols produced by one individual awakens in the mind of another mental auditory perceptions of sound varying in pitch, duration, and loudness.  Complex neuro-muscular mechanisms preside over these two functions of the vocal instrument.  The instrument is under the control of the will as regards the production of the notes in loudness and duration, but not so as regards pitch; for without the untaught instinctive sense of the mental perception of musical sounds correct