The distinction between friction sounds and dry rales is some-
times difficult to make. It may be remarked that rales are changed
by coughing, friction sounds are not ; that friction sounds are in-
creased in intensity by the pressure of the stethoscope, and that
under these circumstances a complaint of pain is made ; that
friction sounds are appreciable to the hand.
They may be compared to the creaking of new soles and to the
rustling of a tense sail.
Pectoral Fremitus

Pectoral or vocal fremitus is appreciated by placing the
hands symmetrically on the two sides of the chest while the
patient speaks or counts in a deep voice. In healthy persons
one feels a distinct vibration of the chest-wall produced by
the conduction of the voice.
VI DISEASES OF THE RESPIRATORY TRACT 141

Pectoral fremitus is increased in pneumonia, above pleu-
ritic effusions, in cavities with thickened walls. (Infiltrated
and compressed tissues are good conductors of 'sound ; in
cavities the sound of the voice is intensified by reflection
from the walls.)

Vocal fremitus is diminished or absent : —

a. When the pleural sac is filled with fluid or with air

(pleurisy and pneumothorax). Over pleural adhe-
sions, vocal fremitus is frequently well preserved.
b. When the large bronchi are occluded by tumors or

stenosis.
The diminished intensity or absence of vocal fremitus
is of diagnostic value only when the voice is strong and
deep. A weak voice produces a weak fremitus. In very
stout people, it can not be well felt.
