426 DISEASES OF THE RESPIRATORY ORGANS. 



tapping on the surface of tlie body with a view to determine 

 the healthy or morbid condition of the parts beneath. The 

 immediate object determined by percussion is the comparative 

 density of subjacent parts. This tapping or percussing may 

 be executed by directly striking the chest with the fingers or 

 hand, or with an object held in the hand, then termed imme- 

 diate; or indirectly mediatehj, when some object is interposed 

 between the hand, or object held in the hand, and the wall of 

 the chest. In mediate percussion the intervening body is 

 termed a ' pleximeter :' it is generally a piece of thin ivory, 

 bone, or vulcanite, or the middle finger of the left hand may 

 be used for the purpose. 



In our patients, the most convenient and the simplest mode 

 of percussion, at least with the larger, is ' immediate,' performed 

 by striking the surface with the tips of the fingers or the 

 knuckles of the closed hand. In carrying out this tapping or 

 percussing some points require to be attended to. When the 

 percussion is immediate, it is desirable to choose for the part 

 to be struck the surface of a rib where this is possible, and to 

 strike it perpendicularly, not slantingly; also to deliver the 

 blow Avith the same amount of force all over the region per- 

 cussed, that the sound may be as uniform as possible. When 

 an intervening body is employed, whether the finger or a 

 pleximeter, in ' mediate ' percussion, it ought to be applied 

 closely to the surface and steadily pressed to the parts that 

 air may be prevented from passing between it and the body- 

 surface, by which the sound would be modified. In this way 

 also we compress the subcutaneous fat, rendermg it more con- 

 ducting, and lesson the distance between the surface and the 

 organ being examined. 



5. Auscultation. — ^By this we mean to indicate the means 

 whereby we obtain knowledge of the state of internal organs 

 by the sound conveyed to the ear ; it is listening to the sounds 

 of the interior by the ear applied to the surface. 



Like percussion, auscultation may be performed directly and 

 immediately by placing the ear upon the surface, merely inter- 

 23osing, on the score of cleanliness, a handkerchief or piece of 

 thin calico ; or mediately by the use of an instrument, the 

 ' stethoscope,' Avhich, besides circumscribing the area examined, 

 assists in conveying the sound from the body to the ear. Some 



