18 DISEASES OF THE HOBSE. 



The manner in which the horse coughs is of importance in diagno- 

 sis. The cough is a forced expiration, following immediately upon a 

 forcible separation of the vocal cords. The purpose of the cough is 

 to remove some irritant substance from the respiratory passages, and 

 it occurs when irritant gases, such as smoke, ammonia, sulphur vapor, 

 or dust, have been inhaled. It occurs from inhalation of cold air if 

 the respiratory passages are sensitive from disease. In laryngitis, 

 bronchitis, and pneumonia, cough is very easily excited and occurs 

 merely from accumulation of mucus and inflammatory product upon 

 the irritated respiratory mucous membrane. If one wishes to deter- 

 mine the character of the cough, it can easily be excited by pressing 

 upon the larynx with the thumb and finger. The larynx should be 

 pressed from side to side and the pressure removed the moment the 

 horse commences to cough. A painful cough occurs in pleurisy, also 

 in laryngitis, bronchitis, and bronchial pneumonia. Pain is shown 

 by the effort the animal exerts to repress the cough. The cough is 

 not painful, as a rule, in the chronic diseases of the respiratory tract. 

 The force of the cough is considerable when it is not especially pain- 

 ful and when the lungs are not seriously involved. When the lungs 

 are so diseased that they can not be filled with a large volume of air, 

 and in heaves, the cough is weak, as it is also in weak, debilitated 

 animals. If mucus or pus is coughed out, or if the cough is accom- 

 panied by a gurgling sound, it is said to be moist; it is dry when 

 these characteristics are not present — ^that is, when the air in passing 

 out passes over surface not loaded with secretion. 



In the examination of the chest we resort to percussion and aus- 

 cultation. When a cask or other structure containing air is tapped 

 upon, or percussed, a hollow sound is given forth. If the cask con- 

 tains fluid, the sound is of a dull and of quite a different character. 

 Similarly, the amount of air contained in the lungs can be estimated 

 by tapping upon, or percussing, the walls of the chest. Percussion is 

 practiced with the fingers alone or with the aid of a special percus- 

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

 If the fingers are used, the middle finger of the left hand should be 

 pressed firmly against the side of the horse and should be struck with 

 the ends of the fingers of the right hand bent at a right angle so as to 

 form a hammer. The percussion hammer sold by instrument makers 

 is made of rubber or has a rubber tip, so that when the pleximeter, 

 which is placed against the side, is struck the impact will not be 

 accompanied by a noise. After experience in this method of exami- 

 nation one can determine with a considerable degree of accuracy 

 whether the lung contains a normal amoimt of air or not. If as in 

 pneumonia, air has been displaced by inflammatory product occupy- 

 ing the air space, or if fluid collects in the lower part of the chest, the 

 percussion sound becomes dull. If, as in emphysema, or in pkeu- 



