ir_) is about 100 cubic inches.

5. The quantity that can be expelled after the most forcible
inspiration--_i.e._, the amount of air that can be moved--indicates
the _vital capacity_. This varies very much with the individual, and
depends not a little on the elasticity of the chest walls, and so
diminishes with age. It follows that youth is the best period for the
development of the chest, and the time to learn that special
breath-control so essential to good singing and speaking.

When the ribs have been raised by inspiration and the abdominal organs
pressed down by the diaphragm, the chest, on the cessation of the act,
tends to resume its former shape, owing to elastic recoil quite apart
from all muscular action; in other words, inspiration is active,
expiration largely passive. With the voice-user, especially the
singer, expiration becomes the more important, and the more difficult
to control, as will be shown later.

It must now be apparent that such use of the voice as is necessitated
by speaking for the public, or by singing, still more, perhaps, must
tend to the general welfare of the body--_i.e._, the hygiene of
respiration is evident from the physiology. Actual experience proves
this to be the case. The author has known the greatest improvement in
health and vigor follow on the judicious use of the voice, owing
largely to a more active respiration. It also follows, however, that
exhaustion may result from the excessive use of the respiratory
muscles, as with any others, even when the method of chest-expansion
is quite correct. Before condemning any vocal method one does well to
inquire in regard to the extent to which it has been employed, as well
as the circumstances of the voice-user. A poor clergyman worried with
the fear of being supplanted by another man, or a singer unable to
secure employment, possibly from lack of means to advertise himself,
is not likely to grow fat under any method of vocal exercise, be it
ever so physiological; while the prima donna who has chanced to please
the popular taste and become a favorite may "wax fat and kick."

[Illustration: FIGS. 14, A and B, are to be compared: that on the left
shows the position of the diaphragm, abdominal walls, etc., during
expiration; the one on the right, during inspiration. The relative
quantities of air in the chest in each case are approximately
indicated by the shaded areas.]

CHAPTER IV.

BREATHING FURTHER CONSIDERED THEORETICALLY