26 CLINICAL DIAGNOSTICS. 



2. If an air-containing organ is set in vibration it pro- 

 duces a sound of considerable intensity, duration and tone, 

 the so-called resonant sound. 



The clearness of the sound depends upon the volume of 

 the air-containing organ which is vibrating. 



a. The stronger the percussion the larger is the part 

 which vibrates and the fuller the sound (Fig. 2). 



b. The thinner the over-lying tissue of the thoracic wall 

 the more lung tissue will vibrate and the fuller the sound 

 (Fig. 3). 



c. If the volume of the air-containing organ is small in 

 itself then the sound is correspondingly less intensive (Fig. -4). 



This explains the varying intensity of the sound over dif- 

 ferent portions of the chest wall when the percussion blows 

 are applied with equal force. The resonant sound gradually 

 merges into the dull femoral as we approach the forward and 

 upper portions. 



The resonant sound may be divided into : 



1. The tympanitic sound which is emitted when the 

 vibrations of the tissue are uniform. It approaches a musical 

 sound and is, therefore, spoken of as a tympanitic tone. 



2. The full sound which is emitted when the vibrations 

 of the tissue are not uniform. It lacks the musical quality of 

 the tympanitic tone and approaches a noise. 



The tympanitic tone and the full sound merge into each 

 other gradually. The sound between is called "over-full'' or 

 "over-loud." 



The tympanitic tone and the full sound are resonant in 

 character. They may become modified as to clearness until 

 they are absolutely dull (flat). The intermediate stages are 

 dull resonant and dull tympanitic. 



