44 DISEASES OF THE TRACHEA 



CHRONIC TRACHEITIS AND BRONCHITIS. 



Definition.— This is a chronic inflammation of the mucous 

 membrane of the trachea and bronchial tubes. 



Etiology.— Chronic tracheitis and bronchitis may occur 

 independently or secondary to some other disease. It may 

 originate from any of the causes of acute tracheitis and 

 bronchitis, especially when their action is persistent or fre- 

 quently repeated. The common causes are: 



(a) Continued inhalation of irritating dust, dirt, etc. 



(b) Exposure to cold, damp air (as keeping animals in 

 cold, damp basements having poor ventilation). 



(c) Parasitic. In severe infestations with Ankylostoma 

 canina, when the animal is being constantly reinfested, the 

 passage of the larvse through the tracheal and bronchial 

 structure produces a chronic irritation. (See Uncinariasis.) 

 Chronic tracheitis and bronchitis often result from the 

 gradual extension of the inflammatory process from the 

 other parts (laryngitis, pharyngitis, etc.). Many cases are 

 secondary to special diseases such as distemper, carcinoma, 

 sarcoma, rachitis and acute valvular insufficiency. 



Pathology.— Chronic tracheitis and bronchitis are practi- 

 cally always purulent, and while in most particulars it 

 closely resembles the acute form, it differs from it in the 

 presence of a more deeply penetrating inflammation and in 

 the production of fibrous tissue. The mucous membrane 

 is swollen, reddened, infiltrated, and covered with purulent 

 secretion. The walls of the bronchi are hypertrophic. Not 

 infrequently the mucosa is thrown into little polypoid excres- 

 cences, due partly to contraction and partly to fibrous prolif- 

 eration. The walls of the bronchi become thickened and 

 there is often a fibrous peribronchitis, which in time may 

 lead to induration of the lungs. 



Symptoms.— This condition is most common in old animals 

 where it frequently interferes with respiration producing 

 so-called asthma. The most prominent symptom of this dis- 

 ease is the cough. It is usually moist, varying in intensity, 

 depending upon the amount of secretion and extent of mucous 

 membrane involved. Excitement frequently produces par- 



