82 DISEASES OF THE LUNGS. 



guous to the diaphragm ; whereas in man, the stomach alone partly lies 

 within the boundaries of the chest : these holloAv viscera necessarily affect- 

 ing the sounds elicited by percussion of the posterior or inferior parts 

 of the chest. Had M. Leblanc taken these anatomical differences into 

 account, he would not have allowed himself to run into error as he has 

 done. 



The SOUND OBTAINED BY PERCUSSION is loudcst in the middle region, 

 between the 7th, 8th, and 9th ribs. From this to the 15th rib it 

 diminishes ; but again increases from this all the way to the last rib. 

 Along the right superior region the sound grows louder from the poste- 

 rior border of the shoulder to the last rib ; whilst on the left side it gra- 

 dually diminishes along the same line. This difference cannot be explained 

 but from the circumstance of the arch of the colon projecting so far into 

 the chest, this being particularly observable in long-carcased horses. It 

 shows the incorrectness of Leblanc's general rule for ascertaining the 

 nature of sounds, viz. comparing those of the two sides. In the inferior 

 reo'ion, the sound obtained upon the 6th rib may be compared to that of 

 the superior region behind the shoulder : this holds as far as the 9th rib, 

 from which point to the last rib the sound gradually lessens, until it 

 becomes abdominal. On the right side the sound is found somewhat 

 duller, on account of being opposed by the liver. After all, however, 

 what with the shoulder and the different muscles clothing the chest, and 

 the cartilages of the ribs, which themselves afford little or no sound, there 

 is really not more than a third of the- chest of the horse available for the 

 purposes of effectual percussion ; a fact which may very well explain the 

 little advantage veterinarians have hitherto derived from the practice of 

 it. The chests of old animals afford more sound than those of middle- 

 aged, and these latter than those of young subjects : differences owing 

 to diminished density of lung and more stability of rib in the aged 

 animal. Lean horses, or such as are empty-bowelled, afford more sound 

 than fat ones, and such as have full stomachs. 



We are not to suppose that it is enough to have made ourselves 

 acquainted with the variations of sound of the healthy chest, in order to 

 understand those of disease : much practice is required to estimate the 

 value of sounds ; and, after all, percussion itself is often insufficient, un- 

 aided by auscultation. 



The resonance of the healthy chest may be augmented, diminished, or 

 annihilated. It is augmented throughout the posterior lobes of the lungs 

 when they are emphysematous. Effusion into one pleural sac augments 

 the sound of the opposite one : that lung being compelled to admit more 

 air, becomes more resonant. It is diminished during congestion, inflam- 

 mation of the parenchyma, and tuberculous phthisis, when much of the 

 luno- is diseased. The sound is lost or becomes dead under effusions. 

 This deadness may be on one or both sides, or may be confined — as is 



