performing the act of breathing. The diaphragm acts like the piston of
a pump, both on the lungs above, and on the contents of the abdominal
and pelvic cavities below. When it rises from B to A, it diminishes
the size of the thoracic cavity, compresses the lungs, and assists in
the expiratory part of breathing; at the same time it acts through the
contents of the abdominal cavity on the pelvic roof, D, to which the
uterus is attached, and raises it from D to C. When the diaphragm
contracts, it descends from A to B, increases the size of the thoracic
cavity, inflates the lungs, promotes the inspiratory part of
breathing, pushes the walls of the chest and abdomen outward from F to
E, and lowers the pelvic roof at the same time the uterus sinks from C
to D. When the effect of these respiratory motions is not diminished
by muscular debility, rigidity of the thoracic walls, or by unsuitable
clothing, they have so direct an effect on the pelvic contents that
the uterus and its appendages make two distinct motions every time a
woman breathes. When the diaphragm rises and the breath is expelled,
the womb is elevated from one inch to one inch and a half, because the
roof of the pelvis, to which it is attached, is lifted about this
distance, because of gentle suction from above. The uterus and its
appendages are thus kept in constant motion, up and down, chiefly by
action of the muscles by which breathing is carried on.

Several influences combine to maintain the circulation of the blood.
The pumping action of the heart and the affinity of the blood for the
walls of the capillary vessels require to be assisted by the motion
both of the body as a whole and of its parts in order to keep the
circulation flowing equably through every tissue. Therefore muscular
action and the resulting bodily motion play a very important part in
maintaining the general and local blood circulation. During the
contraction of a muscle, the blood current flowing through it is, for