KXAMINATION OF THE RE.SPIIiATORY APPARATUS. 315 



Thorax. The thorax can lie examined 1)y inspection, palpation, 

 percussion, and auscultation. 



By inspection we discover whether the formation of the thorax 

 as a ^Yhole is normal, or whether there exist congenital or acquired 

 deformities, asymmetry like that produced by pneumo-thorax or devia- 

 tions of ribs from the normal line, etc. One also notes the breathing- 

 movements, the manner in which the sides expand and contract, the 

 respiratory rhythm, and any special peculiarities of inspiration or 

 expiration. 



Palpation reveals the degree of sensitiveness of the thoracic wall and 

 of the intercostal spaces, the existence of more or less extensive local 

 cedematous infiltration, and the presence or disappearance of thoracic 

 conditions like hydro-thorax. 



Percussion indicates the degree of sonority of the chest in different 

 parts. It can either be practised directly with the hand or through the 

 medium of a pleximeter. The latter method is preferable when 

 dealing with fat animals. Percussion, however, gives slightly different 

 results, according to the degree of fatness of the subjects. It should be 

 practised both in a vertical as well as in a horizontal direction. 



At all points where the muscles are thick or well developed the results 

 produced are negative, in the sense that only a dull sound is obtained. 

 This is the result obtained in auscultating the areas marked 1, where 

 one meets with the ileo-spinal and common intercostal muscle, and in 

 that marked i, where the olecranian muscles are encountered (Fig. 166). 

 Over the middle and inferior zones, however, the results are much more 

 instructive. 



On the right side percussion of the middle zone gives, under normal 

 conditions, a clear sound and perfect resonance from above downwards, 

 and from in front backwards, between the fourth intercostal space and 

 the ninth rib. Beyond this point lies the liver, which gives a partial 

 dull sound, and absolute dulness from the ninth to the twelfth rib, in 

 consequence of its position, and of the projection of the dia]3hragm 

 towards the thoracic cavity. 



Percussion of the inferior zone produces less marked resonance, which 

 diminishes more and more towards the base, in consequence of the thin- 

 ness of the pulmonary lobes at this point. This resonance does not 

 extend as far as the hypochondriac region, because the lower part of the 

 abomasum insinuates itself beneath the costal cartilages and causes a 

 region of dulness. 



On the left side percussion gives precisely similar results, except 

 in the upper portion of the middle zone. Beyond the ninth inter- 

 costal space the sound changes, and has a tympanic character ; because 

 here the anterior and upper portions of the rumen are encountered, 



