ight angle so as to form a
hammer. The percussion hammer sold by instrument makers is made of
rubber or has a rubber tip, so that when the pleximeter, which is placed
against the side, is struck the impact will not be accompanied by a
noise. After experience in this method of examination one can determine
with a considerable degree of accuracy whether the lung contains a
normal amount of air or not. If, as in pneumonia, air has been displaced
by inflammatory product occupying the air space, or if fluid collects in
the lower part of the chest, the percussion sound becomes dull. If, as
in emphysema, or in pneumothorax, there is an excess of air in the
chest cavity, the percussion sound becomes abnormally loud and clear.

Auscultation consists in the examination of the lungs with the ear
applied closely to the chest wall. As the air goes in and out of the
lungs a certain soft sound is made which can be heard distinctly,
especially upon inspiration. This sound is intensified by anything that
accelerates the rate of respiration, such as exercise. This soft,
rustling sound is known as vesicular murmur, and wherever it is heard it
signifies that the lung contains air and is functionally active. The
vesicular murmur is weakened when there is an inflammatory infiltration
of the lung tissue or when the lungs are compressed by fluid in the
chest cavity. The vesicular murmur disappears when air is excluded by
the accumulation, of inflammatory product, as in pneumonia, and when the
lungs are compressed by fluid in the chest cavity. The vesicular murmur
becomes rough and harsh in the early stages of inflammation of the
lungs, and this is often the first sign of the beginning of pneumonia.

By applying the ear over the lower part of the windpipe in front of the
breastbone a somewhat harsh, blowing sound may be heard. This is known
as the bronchial murmur and is heard in normal conditions near the lower
part of the trachea and to a limited extent in the anterior portions of
the lungs after sharp exercise. When the bronchial murmur is heard over
other portions of the lungs, it may signify that the lungs are more or
less solidified by disease and the blowing bronchial murmur is
transmitted through this solid lung to the ear from a distant part of
the chest. The bronchial murmur in an abnormal place signifies that
there exists pneumonia or that the lungs are compressed by fluid in the
chest cavity.

Additional sounds are heard in the lu