Percussion. 163 



chest only, but the tenderness on pressure and the absence of any 

 crepitation serve to distinguish the case from pneumonia. In the 

 smaller animals the position of the dulness may be altered by 

 turning the patient on its back as the water always gravitates to 

 the lowest point. 



The presence of extensive deposits of tubercle, of cretaceous ma- 

 terial in tubercular cows and sheep, and the presence of large 

 cysts in the lung may give rise to dullness over a circumscribed 

 area. Such areas of dullness are usually multiple with sound lung 

 between. 



A further modification known as the cracked pot sound is 

 sometimes heard in horses and cattle. It may be aptly repre- 

 sented by laying the palms of the two hands together in such a 

 way that they meet all round and leave an interval filled with air 

 right in the centre. The back of the one hand is then struck 

 against the knee when the noise of the air escaping gives the 

 characteristic sound. It occurs in consumption or in the ad- 

 vanced stages of inflamed lungs when a large tubercle or abcess 

 has burst into a bronchial tube and the resulting cavity opens 

 into this tube by a narrow orifice. 



