[Illustration: The course and distribution of the Hypoglossal or Ninth pair of nerves; the deep-seated nerves of the neck are also seen: 1, the hypoglossal nerve; 2, branches communicating with the gustatory nerve; 3, a branch to the origin of the hyoid muscles; 4, the descendens noni nerve; 5, the loop formed with the branch from the cervical nerves; 6, muscular branches to the depressor muscles of the larynx; 7, a filament from the second cervical nerve, and 8, a filament from the third cervical, uniting to form the communicating branch with the loop from the descendens noni; 9, the auricular nerve; 10, the inferior dental nerve; 11, its mylohyoidean branch; 12, the gustatory nerve; 13, the chorda tympani passing to the gustatory nerve; 14, the chorda tympani leaving the gustatory nerve to join the submaxillary ganglion; 15, the submaxillary ganglion; 16, filaments of communication with the lingual nerve; 17, the glosso-pharyngeal nerve; 18, the pneumogastric or par vagum nerve; 19, the three upper cervical nerves; 20, the four inferior cervical nerves; 21, the first dorsal nerve; 22, 23, the brachial plexus; 24, 25, the phrenic nerve; 26, the carotid artery; 27, the internal jugular vein.]
The study of the functions of the cranial nerves convinces me that the state of mind which conceives a tone acts upon the organs of speech through the cranial nerves in a way to give vocal expression. In perfect expression the conception and the expression are absolutely synchronous.
In the production of a good tone there is an exact relation between pitch and resonance. This relation is provided for in nature and a disobedience to it brings an unpleasant quality into the voice. This is true in both speech and song, for the speaking and singing voices rest upon the same fundamental principles. Speech is one application or use of the voice, song is another. The voice of true speech is as melodic as the voice of song. There are, however, many persons who use their voices better when they sing than when they speak, while others use their voices better in speaking than in singing.
There is a difference between tone and noise. Voice is produced by a succession of vibrating waves of air. In a musical tone the waves are regular in their succession; in noise they are irregular.