g the "vital capacity,"
is about 225-250 inches.

The chest is enlarged by the muscles of inspiration, the principal of
which is the diaphragm or midriff. This muscle (tendinous in the
centre) is attached to the spinal column (behind) and to the last six
or seven ribs. When it contracts it becomes less domed upward, and is
pressed down more or less on the contents of the abdomen; hence the
walls of the latter move outward. During ordinary inspiration the
lower ribs are steadied by other muscles, so that no indrawing of
these ribs takes place, but a very forcible expiration makes such
indrawing very noticeable. In addition to the enlargement of the chest
by the descent of the diaphragm, the ribs are elevated and everted by
the muscles attached to them, with the total result that the chest
cavity is enlarged in all its three diameters during inspiration. The
first rib is fixed by muscles from above. During extremely forced
inspiration a large proportion of all the muscles of the body may act.
Ordinary expiration is the result largely of the elastic recoil of the
chest walls, only a few muscles taking part. The diaphragm ascends and
becomes more domed. During forced expiration many other muscles are
called into action. It is of importance for the singer and speaker to
note: (1) That the chest cavity should be increased in all its
directions; (2) that the muscular action should be easy and under
perfect control, but also vigorous when required; (3) that the breath
be taken through the nostrils when the individual is not actually
vocalizing or about to do so; (4) that the breath be kept in or let
out in the proportion required.

Breathing is a reflex or involuntary act. The respiratory centre,
consisting of an expiratory and inspiratory division, is situated in
the bulb, or medulla oblongata, the portion of the brain just above
the spinal cord. All the ingoing nervous impulses affect respiration
through the outgoing impulses that pass along the nerves to the
muscles; that is, the ingoing impulses pass up by the nerves from the
lungs to the centre, and thence along other nerves to the respiratory
muscles. The condition of the blood determines the activity of the
respiratory centre, but the incoming impulses regulate this activity.
The respiratory centre can be approached from every part of the body.

_Hygiene._

Every thing that favors the full and free expansion of the chest in a
pure atmosphere is favorable, and the