DETEI^MINING THE STATUS PRATESENS. 37 



The resonant sound may be subdivided into: 



1. The tympanitic sound, which approaches a musical 

 tone. 



2. The full sound (puhiionary resonance). 



The tympanitic and full sounds are both resonant in char- 

 acter, and in both the degree of clearness can vary until they 

 become identified with the dull sound. The intermediate 

 stages are comparatively duUcd and dull tympanitic. 



Occurrence of the Different Qualities of Percussion- 

 Sounds. 



According to the above classification there are three kinds 

 of percussion-sounds; The full (pulmonary resonant), the 

 tympanitic, and the flat. 



1. The full sound is found over normal lung, the air in 

 the alveoli, and the lung tissue, and thoracic walls vibrating. 

 When the intestines are so distended with gas that when per- 

 cussed their walls vibrate with their contents, a full sound is 

 emitted. 



2. The tympa)iiiic percussion-sound has a varied origin. 

 It is heard: 



2,. Over cavities containing air which communicate with 

 the outside world, their walls being either firm 'or yielding: 

 trachea, caverns in the lung communicating with bronchi. 

 The pitch of the sound depends upon the size of the cavern 

 and its communicating opening. 



b. Over enclosed air-containing cavities the walls of 

 which are little distended, hence over the stomach and bowels. 



c. Over lung tissue the tension of which has become 

 diminished, (atelectasis, beginning hepatization). 



3. The Hat (femoral, dull) sound is heard when percuss- 

 ing over solid tissues which do not contain air. As the most 

 forcible percussion does not produce vibrations at a point more 

 than 10cm below the surface, dullness can be noted over the 



