36 DISEASES OF THE TRACHEA 



in most cases develop from bacteria found normally on the 

 mucous membrane. 



Pathology . The pathological changes that are liable to 

 be found in acute tracheitis and bronchitis are somewhat 

 diverse, the details of the process being considerably modified 

 by the anatomical peculiarities of the parts affected and the 

 different causes that affect them. The inflammation may 

 be restricted to the bronchial structure but is frequently 

 associated with other and more serious disturbances. The 

 condition is usually bilateral, although certain parts are 

 affected more than others. Tracheitis and bronchitis are 

 often associated with laryngitis, peribronchitis and broncho- 

 pneumonia. 



Symptoms. Coug h. This is the most important symptom 

 and is never absent, although it may be slight or very severe 

 and loud, occurring as isolated coughs succeeding each other 

 with greater or less frequency, or in paroxysms which often 

 end in nausea or vomiting. The cough is dry and harsh in 

 the early stages, later becoming moist as the inflamed mucous 

 membranes produce an increased secretion. Paroxysms of 

 coughing are often induced by excitement (visits of the owner, 

 etc.), exposure to cold, moist air, pressure over the lower part 

 of the trachea or by percussion over the sides of the chest. 

 The object of the cough is to expel the accumulated discharge 

 from the air passages. 



Discharge, This is always present except in the early 

 stages; it is mucous at first, becoming mucopurulent or puru- 

 lent as the disease progresses. In small animals the discharge 

 is expelled from the trachea and bronchi directly into the 

 mouth and swallowed. Therefore it is impossible to deter- 

 mine the amount and character, and it becomes necessary 

 to observe the animal while coughing to ascertain the condi- 

 tion of the discharge. 



Dyspnea. The degree of dyspnea depends on the obstruc- 

 tion of the free movement of air through the bronchial tubes. 

 In mild cases it may not be noticed but in other cases, in 

 which the calibre of the bronchi is materially decreased by 

 the swelling of the mucous membrane, it may be quite dis- 

 tressing. 



