AUSCULTATION. 499 



of its own, which render it applicable on particular occasions. 

 As a general rule, direct application of the ear is to be pre- 

 ferred, and for several reasons. It can at all times be readily 

 resorted to; the ear is applied closer to the organ examined, 

 and will hear the sounds more distinctly ; and the chest of 

 the patient affords a support for the head of the operator, 

 who thereby avoids the necessity of holding it in a con- 

 strained position, which would distract his attention. The 

 stethoscope is useful when we are anxious to localize the 

 sound, or when the surface is depressed, and prevents the 

 accurate adaptation of the ear, as close behind or in front of 

 the shoulder. 



Percussion. This consists in striking upon the surface, 

 with the, view of eliciting sounds, whereby we may form 

 an opinion as to whether the subjacent organs are in a 

 healthy or morbid condition. Not only do we learn from 

 the sounds in such cases, but when liquid is contained in the 

 part, a vibratory movement is imparted by the stroke, and in 

 certain instances, such an examination may draw forth indi- 

 cations of pain, which could not be produced by pressure or 

 otherwise. The sounds correspond with the condition of 

 the subjacent parts. Thus, when a large hollow cavity, as the 

 distended first stomach of cattle, is percussed, it is very 

 resonant or tympanitic. In the abdomen of the horse, 

 in ordinary cases, the resonance is much less. Again, in 

 the case of the lungs, with their myriads of minute air-cavi- 

 ties, it is even less noticeable, though still well marked, while, 

 when a thick and solid part is struck, the sound is dull or 

 flat Even with solid organs, degrees of resonance may be 

 observed; thus a firm, unyielding body, like bone or carti- 

 lage, resounds more than soft structures, as fat or muscle. 

 When percussing a fat animal, accordingly, allowance must 

 be made for this non-conducting character of adipose tissue, 



