NONCONTAGIOUS DISEASES OF RESPIRATION ORGANS. 91 



are distinct or indistinct, depending upon tiie quantity of fluid that 

 is present and the size of the tubes in which the sound is produced. 

 According to their character they are divided into dry and moist. 

 The friction sound is produced by the rubbing together of roughened 

 surfaces and is characteristic of pleurisy. 



Percussion. — Percussion is that mode of examination by which we 

 elicit sounds by striking or tapping over the part. It may be direct 

 or indirect. If the middle finger of the left hand is placed firmly on 

 the chest and smartly tapped or struck with the ends of the first three 

 fingers of the right hand, the sound will be noticed to be more reso- 

 nant and clear than when the same procedure is practiced on a solid 

 part of the body. This is because the lungs are not solid, but are 

 always, in health, well expanded with air. But in certain pulmonary 

 diseases, as in pneumonia, they fill up and become solid, when the 

 sound given out by percussing theni is dull, like that on any other 

 solid part of the animal. When fluid has collected in the lower part 

 of the chest cavity the sound will also be dull on percussion. Wliere 

 there is an excess of air in the chest cavity, as in emphysema or in 

 pneumothorax, the percussion sound becomes abnormally loud and 

 clear. By practice on healthy animals the character and boundaries 

 of the sounds can be so well determined that any variations from 

 them will be readily detected, and will sometimes disclose the pres- 

 ence of a diseased condition when nothing else will. 



Percussion is sometimes practiced with the aid of a special percus- 

 sion hammer and an object to strike upon known as a pleximeter. A 

 percussion hammer is made of rubber or has a rubl>er tip, so that 

 when the pleximeter, which is placed against the side of the animal, 

 is struck the impact will not be accompanied by a noise. A percus- 

 sion hammer and pleximeter can be purchased from any veterinary 

 instrument maker. 



CATARRH (cold IN THE HEAd). 



Nasal catarrh is an inflammation of the mucous membranes of the 

 nostrils and upper air passages. Simple catarrh is not a serious disease 

 in itself, but if neglected is liable to be complicated with laryngitis, 

 bronchitis, pneumonia, pleurisy, and other diseases of the respirator}'' 

 organs, which are of a serious nature and sometimes fatal. Catarrh 

 is a common disease among cattle. It is often due to sudden exposure 

 to wet and cold after they have been accustomed to shelter. It may 

 arise from inhalation of irritating gases. It is sometimes due to 

 certain specific atmospheric conditions, and may assume an enzootic 

 form. It is very debilitating, and requires prompt and judicious 

 treatment. 



Siym-ptoms. — Redness of the mucous membranes of the nose, redness 

 and watering of the eyes. The mucous membrane first becomes dry ; 



