PERCUSSION. 



Methods. Tissues as good and bad conductors of sound. Immediate, 

 mediate percussion. Bilateral symmetry and divergence. Effect of build- 

 ing, race, etc. Horse, left side, right. Ox, left side, right. Effect of ist 

 and 3d stomachs, liver, etc. Sheep, diaphragm, Heart. Pig, fat, lean, heart. 

 Dog, method. Birds, back, ribs. In disease, increase, decrease, absence of 

 resonance, in large area, in patches. Crack pot sound. 



This consists in striking the walls of the chest so as to bring out 

 the resonance of the parts. In proportion as we tap gently with 

 the tip of the finger or strike forcibly with the closed fist will we 

 elicit the sounds from the superficial or the deeper parts of the 

 lung. Hence slight blows only must be used when the lung tis- 

 sue is thin, to avoid bringing out the resonance from the deeper 

 seated organs, and both must be resorted to when the lung is thick 

 to ascertain its condition at the various depths. Where a mode- 

 rate force is requisite the four fingers and thumb of the right hand 

 are brought together in a line and the weight of the hand as moved 

 from the wrist is employed to bring out the sound. The ribs be- 

 ing hard convey sound best from the deeper parts, and on them 

 percussion is usually made. Care should be taken not to mistake 

 the lesser resonance conveyed through the soft tissues of the in- 

 tercostal spaces for an indication of a diseased condition. In pro- 

 portion too as the ribs are covered with flesh or fat, the resonance 

 will be diminished and a stronger blow will be necessary to bring 

 out the sound from the lungs. 



If the blow is made directlj"^ on the side of the chest the percus- 

 sion is called immediate ; if made upon an elastic solid body 

 (pleximeter) laid on the outside of the chest it is mediate. The 

 readiest and perhaps the best pleximeter is the middle finger of the 

 left hand which is to be applied flat upon the side of the chest to 

 receive the blow directed perpendicularly to its surface. In fat 

 or fleshy subjects it should be pressed firmly on the surface so as 

 to compress and condense the soft parts and render them better 

 conductors of sound. Some use flat pieces of ivory, silver, caouch- 

 ouc but in employing these the nails of the right hand must be 

 carefully pared, lest by striking the solid body they produce a 

 sound which interferes with the true pulmonary resonance. 

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