expanded, and seeing the frequency with which tubercle occurs in this
region, it might by improving the circulation and nutrition be even
beneficial. The proper mode of breathing comes almost natural to some
individuals; to others it requires patient cultivation under a teacher who
understands the art of singing and the importance of the correct methods of
breathing.

The more powerfully the abdominal muscles contract the laxer must become
the diaphragm muscle; and by the law of the reciprocal innervation of
antagonistic muscles it is probable that with the augmented innervation
currents to the expiratory centre of the medulla there is a corresponding
inhibition of the innervation currents to the inspiratory centre (_vide_
fig. 18, page 101). These centres in the medulla preside over the centres
in the spinal cord which are in direct relation to the inspiratory and
expiratory muscles. It is, however, probable that there is a direct
relation between the brain and the spinal nerve centres which control the
costal and abdominal muscles independently of the respiratory centres of
the medulla oblongata (_vide_ fig. 18). The best method of breathing is
that which is most natural; there should not be a protruded abdomen on the
one hand, nor an unduly inflated chest on the other hand; the maximum
expansion should involve the lower part of the chest and the uppermost part
of the abdomen on a level of an inch or more below the tip of the
breastbone; the expansion of the ribs should be maintained as long as
possible. In short phrases the movement may be limited to an ascent of the
diaphragm, over which we have not the same control as we have of the
elevation of the ribs; but it is better to reserve the costal air, over
which we have more voluntary control, for maintaining a continuous pressure
and for varying the pressure.