430 DISEASES OF THE RESPIRATORY ORGANS. 



position, both of the organs contained there, and also of those 

 in the contiguous cavit}^, the abdomen, particularly the relation 

 of these latter to the former. By recollecting these points we 

 can so far understand the variations of the relative resonancy 

 observed in the different sides of the cavity ; for although the 

 sounds elicited by percussion of one side may be considered 

 as tolerably correctly indicating the character of those on the 

 other, in health this will be found in actual practice not wholly 

 correct, seeing these are modified by the position of the heart 

 and of certain of the abdominal viscera. It is also not to be 

 forgotten that other fortuitous circumstances and conditions 

 connected with both thorax and abdomen, and organs con- 

 tained in these cavities, tend to modify sounds elicited by 

 percussion. 



As a rule, it may be said that in health the sounds produced 

 by percussion are most distinct and loudest over those parts 

 least covered by soft tissues, and where the bronchial sounds 

 are most distinct. Over the superior portions of both sides in 

 the horse the sound is clear to the twelfth rib ; after this, on the 

 right side, if the percussion is executed with much force, it 

 becomes more resonant, of a tympanitic character, as if the 

 lung, in its intimate structure, contained an extra amount of 

 air. In all probability this increased resonance proceeds from 

 the proximity of the arch of the colon. 



Behind the twelfth rib, on the left side, although by forcible 

 tapping resonance may be obtained, still it is markedly less 

 than on the right ; so that it is not very far from the truth if 

 we say that on the right side, in the upper third of the chest, 

 the sound gradually increases from behind the shoulder to 

 near the last rib, while on the left side there is a gradual lessen- 

 ing of sound. Over the middle third a good sound is obtain- 

 able in both sides very much similar ; the resonance is probably 

 most marked from the sixth to the twelfth rib, from Avhich it 

 diminishes to the fifteenth,^becoming after this on the left more 

 resonant, and on the right dull from proximity to the liver. 

 The lower third gives out a weaker though clear sound on the 

 right side from the fifth to the eighth rib, when the sound 

 becomes dull over the region of the liver. On the left, about 

 the fifth, sixth, and seventh ribs, little sound is heard, from the 

 space being in great part occupied by the heart ; it may, how- 



