PHYSICAL DIAGNOSIS. 
499 
heard during- inspiration and expiration. It is not often heard 
at the chest. It is caused by drops of fluid falling into a col¬ 
lection on the bottom of the cavity. It may also be caused 
j by the bursting of a bubble on the sides of a cavity, or by the 
imprisonment of a drop of water on the wall of a cavity. 
Metallic tinkling is pathonomonic in pleurisy. 
Percussion is the process of striking a part with the tips 
of the bent fingers, in order to elicit sounds, upon the charac- 
tei of which depends the condition of the tissues underneath. 
It was discovered by Leopold Avenbrugger, a Vienna physi¬ 
cian, who lived from 1722 to 1809. He practiced percussion 
only. He first began the study of sounds as indications of 
morbid character. The idea was introduced into France by 
Corvisart in 1821. Mediate percussion was suggested by 
Piorry in 1828. It is customary in percussion to lay the mid¬ 
dle finger, or two fingers of the left hand, upon the part and 
stroke with the finger-tips of the right hand. Every physi¬ 
cian has his own way of percussing. The striking should be 
a wrist movement, not a forearm movement. The blows 
should not be too heavy and be made with discrimination. 
To percuss well is an art which one can only become profi¬ 
cient in by long practice. Sounds elicited by percussion vary in 
intensity, quality, duration and pitch. Intensity means loud¬ 
ness ; quality, the kind of sound; duration, the length ; and 
pitch, the degree of sound. Percussion sounds are due to 
vibration of air in the air cells, and of the chest walls. Per¬ 
cussion on a healthy subject shows that the results are not 
the same on both sides of the chest. Over the plane of the 
upper third on the right side the sound is the same to the 
eleventh rib back. Over the middle third, on both sides, the 
degree of resonance is about the same from the sixth to the 
twelfth rib. Behind this it is dull on the right side and more 
resonant over the left side. On the lower third percussion is 
clear, back to the tenth rib, where it becomes more dull. On 
the left side, dullness is found over the thirteenth rib back. 
So in the middle portion we find increasing pulmonary 
resonance, and in the superior and inferior portions we find 
diminished pulmonary resonance. 
