oes, however, deem it of the highest importance
that the student should learn by actual observation on his own person
that his chest does expand in each of the three directions indicated
above.

It is not necessary to dissect to observe muscles; in fact, they can
be seen in action only on the living subject. All who would really
understand breathing should study the chest when divested of all
clothing and before a sufficiently large mirror. He may then observe
the following during a fairly deep inspiration:

1. The chest is enlarged as a whole.

2. The abdominal walls move outward.

3. The ribs pass from a more oblique to a less oblique position, and
may become almost horizontal; their upper edges are also turned out
slightly, though this is not so easy to observe.

4. Again, in the case of a very deep and sudden inspiration, the
abdomen and the lower ribs also are drawn inward.

The changes above referred to are brought about in this way:

1. The total enlargement is due to the action of many muscles which
function in harmony with each other.

2. The chief changes are brought about by those muscles attached
between the ribs (_intercostales_); but these act more efficiently
owing to the cooeperation of other muscles which steady the ribs and
chest generally, such as those attached to the shoulder-bones and the
upper ribs; indeed, the most powerful inspiration possible can only be
effected when most of the other muscles of the body are brought into
action. One may observe that even the arms and legs are called into
requisition when a tenor sings his highest tone as forcibly as
possible, though this is often overdone in a way to be condemned. Art
should not be reduced to a gymnastic feat.

The most important muscle of inspiration is the _diaphragm_, or
midriff, because it produces a greater change in the size of the chest
than any other single muscle. Some animals can get the oxygen they
require to maintain life by the action of this large muscle alone,
when all other respiratory muscles are paralyzed. As it is so
important, and above all to the voice-user, it merits special
consideration.

In studying the action of a muscle it is necessary to note its _points
of attachment_ to harder structures, either bone or cartilage. Nearly
always one such point is more fixed than the other, and from this the
muscle pulls when it contracts.

The diaphragm is peculiar in that it is somewhat circular in shape and
is more