The diaphragm separates the cavity of the thorax from the cavity of the
abdomen, and constitutes the floor for the heart and lungs to rest upon,
and also a close-fitting cover for the contents of the abdomen.
Therefore it is evident that the moving of the diaphragm moves the
organs which are immediately above and those below it. In reposeful
breathing the enlargement of the cavity of the chest is chiefly
accomplished by the contraction of the diaphragm. As it contracts it
presses upon the abdominal viscera. The abdominal muscles antagonize the
diaphragm by pressing back the abdominal viscera, thus causing its
ascent as soon as the diaphragm has become relaxed.
As the diaphragm contracts, the air rushes through the nostrils or mouth
to fill the lungs. By lifting the ribs the thorax can be sufficiently
enlarged to meet ordinary demands for breath; therefore the lungs would
not immediately suffer if the diaphragm was not contracted. The
principal sufferers in such a case would be the stomach, liver, and
intestines, for without this exercise which the contraction of the
diaphragm gives them they would not as vigorously perform their
functions.
It is taught in many works on physiology that men inhale by means of the
contraction of the diaphragm chiefly, while in adult women the diaphragm
is exercised little, if any, during respiration. This statement was
first given in early physiologies without due warrant from close
observation. This idea, having once found its way into a standard work,
has continued in successive works until now. This theory is of such
vital interest to all that the authority for it should be carefully
examined. It is a fact that more women than men breathe wholly by means
of elevating and lowering the ribs; it is also a well-observed fact that
the healthiest women and the healthiest men breathe alike, with no
movement of the upper part of the chest during reposeful respiration. It
is only when an unusual amount of air is required that the healthiest
men and women ever move the upper part of the chest during respiration;
then the diaphragm is exercised vigorously, and the movements of the
ribs take place only for the purpose of enlarging the cavity of the
thorax beyond what it is possible for the diaphragm alone to accomplish.
During the last twenty-five years I have cured hundreds of people, both
men and women, of dyspepsia and its attendant weaknesses by teaching
them how to exercise the diaphragm in respiration, and in the production
of tone. To say nothing of the incorrect way in which women breathe, I
find that a majority of men breathe improperly.
The shape of the diaphragm, when it is relaxed, resembles an open
umbrella. When the diaphragm is flattened by contraction it no longer
retains its dome-like shape, and thus gives greater depth to the thorax.
DIFFERENCE IN THE ACTION OF THE DIAPHRAGM
DURING EXPIRATION OF THE BREATH AND
DURING THE PRODUCTION OF TONE.
During expiration of breath the diaphragm is fully relaxed, while during
the production of tone it should be somewhat contracted. In the proper
adjustment of the diaphragm and abdominal muscles during voice
production, the diaphragm by its contraction resists, to some extent,
the pressure caused by the contraction of the abdominal muscles, and
thus only gradually yields to the force brought against it by the
contraction of these muscles, in consequence of which a firm and steady
support is given to the voice.