vocal cords. Those qualities of the voice
which we speak of as sweet, harsh, and sympathetic depend to a great
extent upon the peculiar structure of the vocal cords of the individual.

Besides the physical condition of the vocal cords, as their degree of
smoothness, elasticity, thickness, and so on, other factors determine the
quality of an individual's voice. Thus, the general shape and structure of
the trachea, the larynx, the throat, and mouth all influence the quality
of voice. In fact, the air passages, both below and above the vibrating
cords, act as resonators, or resounding chambers, and intensify and modify
the sounds produced by the cords. It is this fact that prompts skillful
teachers of music and elocution to urge upon their pupils the necessity of
the mouth being properly opened during speech, and especially during
singing.

Experiment 187. _To show the anatomy of the throat_. Study the
general construction of the throat by the help of a hand mirror. Repeat
the same on the throat of some friend.

Experiment 188. _To show the construction of the vocal organs_. Get
a butcher to furnish two windpipes from a sheep or a calf. They differ
somewhat from the vocal organs of the human body, but will enable us to
recognize the different parts which have been described, and thus to get
a good idea of the gross anatomy.

One specimen should be cut open lengthwise in the middle line in front,
and the other cut in the same way from behind.

354. Speech. Speech is to be distinguished from voice. It may exist
without voice, as in a whisper. Speech consists of articulated
sounds, produced by the action of various parts of the mouth, throat, and
nose. Voice is common to most animals, but speech is the peculiar
privilege of man.

[Illustration: Fig. 152.--Diagramatic Horizontal Section of Larynx to show
the Direction of Pull of the Posterior Crico-Arytenoid Muscles, which
abduct the Vocal Cords. (Dotted lines show position in abduction.)]

The organ of speech is perhaps the most delicate and perfect _motor_
apparatus in the whole body. It has been calculated that upwards of 900
movements per minute can be made by the movable organs of speech during
reading, speaking, and singing. It is said that no less than a hundred
different muscles are called into action in talking. Each part of this
delicate apparatus is so admirably adjusted to every other that all parts
of this most complex machinery act in p