tly with thread, so that a chink will be left between them, as shown
in Fig. 154. Force the air through such a tube by blowing hard, and if
the strips are not too far apart a sound will be produced. The sound
will vary in character, just as the bands are made tight or loose.

Experiment 191. "A very good illustration of the action of the
vocal bands in the production of the voice may be given by means of a
piece of bamboo or any hollow wooden tube, and a strip of rubber, about
an inch or an inch and a half wide, cut from the pure sheet rubber used
by dentists.

"One end of the tube is to be cut sloping in two directions, and the
strip of sheet rubber is then to be wrapped round the tube, so as to
leave a narrow slit terminating at the upper corners of the tube.

"By blowing into the other end of the tube the edges of the rubber bands
will be set in vibration, and by touching the vibrating membrane at
different points so as to check its movements it may be shown that the
pitch of the note emitted depends upon the length and breadth of the
vibrating portion of the vocal bands."[51]--Dr. H. P. Bowditch.

[NOTE. The limitations of a text-book on physiology for schools do not
permit so full a description of the voice as the subject deserves. For
additional details, the student is referred to Cohen's _The Throat and
the Voice_, a volume in the "American Health Primer Series." Price 40
cents.]

Chapter XIII.

Accidents and Emergencies.

358. Prompt Aid to the Injured. A large proportion of the accidents,
emergencies, and sudden sicknesses that happen do not call for medical or
surgical attention. For those that do require the services of a physician
or surgeon, much can be often done before the arrival of professional
help. Many a life has been saved and much suffering and anxiety prevented
by the prompt and efficient help of some person with a cool head, a steady
hand, and a practical knowledge of what to do first. Many of us can recall
with mingled admiration and gratitude the prompt services rendered our
families by some neighbor or friend in the presence of an emergency or
sudden illness.

In fact, what we have studied in the preceding chapters becomes tenfold
more interesting, instructive, and of value to us, if we are able to
supplement such study with its practical application to the treatment of
the more common and less serious accidents and emergenc