^8 CLINICAL DIAGNOSTICS 



thick thoracic wall) or if small airless spaces lie amid those 

 containing air (nodular thickenings in the lung). 



During the application of percussion we should note the 

 resistance the part offers to the hammer or striking finger. 

 [To understand what is meant by this the student should 

 strike with the plexor some solid object, as a brick wall, and 

 compare it with the feeling experienced when the human chest 

 is percussed.] By placing the index finger on the back of the 

 hammer the resistance can be better appreciated. From the 

 resistance the amount of vibration that can be induced in the 

 underlying parts may be determined, the greater the former 

 the less developed the latter. For this reason solid, airless 

 parts like muscle give a shallow percussion-sound and cause 

 the hammer to suffer a jar when they are struck. 



Tactile Percussion. 



The combination of palpation and percussion is called 

 tactile percussion. Through this method we endeavor to arrive 

 at the physical condition of deep-lying parts by stroking the 

 tissues covering them. 



Method. The wrist and fingers should be held slightly flexed 

 and fixed. The parts to be examined should be pressed firmly 

 with the finger tips, exerting an interrupted stroke. After such a 

 stroke the fingers should be allowed to dwell for a moment to note 

 the recoil of the underlying tissue the consistency of which we 

 wish. to determine. In practicing this form of percussion bear in 

 mind that the deeper rather than the shallower tissue* are to 

 be felt. 



Tactile percussion may also be practiced with the plexor 

 and pleximeter, the index finger being rested upon the back 

 of the hammer. It is usually better, however, to employ hammer- 

 to-finger or finger-to-finger percussion. 



The thickness of the over-lying fat or muscular layers 

 does not seriously interfere in this •• form of percussion. 

 Through practice we. learn to select the factors of importance 

 to form an opinion. Deep-lying diseased conditions do not 

 present through tactile percussion specific symptoms, but we 

 may thus obtain valuable information in regard to the boun- 



