500 AUSCULTATION. 



and the impulse must be considerably increased. In the 

 same way, when examining a deep-seated organ, or the inte- 

 rior of a bulky one, a greater impulse should be given than 

 when a superficial part has to be tested. 



Percussion may thus enable us to ascertain the presence of 

 air in parts in which it does not normally exist, and likewise 

 the occurrence of solids or liquids where air should normally 

 be, while, by this means, the presence of fluid may be recog- 

 nised in parts which ought to be solid. It may sometimes be 

 advantageously employed along with auscultation, the surface 

 being struck close beside the part where the ear or the stetho- 

 scope is applied. 



Percussion, like auscultation, is either immediate or mediate. 

 The former is effected by simply striking the surface without 

 any intervening body ; in the latter an elastic solid is placed 

 upon the surface, and on which the impulse is sustained. 

 The intervening body is known as a pleximeter. 



There are still some varieties in the method of applying im- 

 mediate percussion. When our larger domestic quadrupeds 

 are the subjects of the operations, and when the deeper parts 

 are to be examined, the closed hand may be employed, and 

 the surface may be struck with the knuckles. When the 

 smaller animals are concerned, or in testing the more super- 

 ficial parts of the larger, the four fingers, with the nails previously 

 pared, may be brought together at the same level, and supported 

 by the thumb, that the requisite impulse may be given with 

 their tips. In some of the smallest of our patients, and when 

 we want delicately to test a superficial part, the middle finger 

 only may be used. In either case the movement should only 

 be from the wrist, since not only is the movement of the fore- 

 arm or whole member clumsy, but the stroke is liable to be 

 too strong or irregular, Where a choice can be made, as in 

 the case of the thorax, the hardest part of the surface (ribs) 



