i8o SYSTEMS OF TREATING STAMMERING

"We can breathe with the ribs or with the diaphragm; with
the former on the principle of the bellows; with the latter on
the principle of the piston. In the former case in Aspiration,
the ribs, by their appropriate muscles, are rolled upward and
outward, enlarging the circumference of the chest; in expira-
tion they return to their former position, partly by their own
elasticity and in part drawn down by the abdominal muscles.
In the latter case, we may breathe with the diaphragm alone;
the muscle which separates the cavity of the chest from that of
the abdomen is attached to the cartilaginous extremity of the
ribs, and, when relaxed, is forced, by the action of the abdom-
inal muscles high up into the cavity of the chest. When it
contracts, it draws straight across the bottom of the chest,
forming a vacuum in the lower part of the chest, into which the
air rushes; again relaxing, the abdominal muscles force it up
into the chest, driving the air before it. In ordinary breathing
we combine these methods.

"In making sound, we expel the air from the lungs upon a
different principle; the diaphragm, instead of relaxing as in
breathing, contracts, and, by diminishing the circumference of
the chest, expels the air as completely from the lungs as in the
other method; in the one, the diaphragm in expiration is pas-
sive, in the other it is active. Both in breathing and in mak-
ing sound, we inspire by contracting the diaphragm, thus caus-
ing a vacuum in the ''bottom of the chest; but we expire upon
a different principle. In ordinary breathing the diaphragm
relaxes, and the abdominal muscles force it up into the chest,
driving the air before it. In making sounds, it continues to
contract, and expels the air by diminishing the circumference
of the chest. This action of the diaphragm is the normal mode
of making sound; it is not necessary to the production of sound,
but is necessary to full, clear, far-reaching sound. Many
persons talk habitually with the diaphragm relaxed, but the