DISEASES OF THE RESPIRATORY SYSTEM. 139 



-the elastic tissue being prominent, the tubes dilated, the glands 

 atrophied, and a wasting of the muscular tissue. 



In other cases the mucous membrane is thick, granular, and 

 infiltrated, and may show erosions. The mucous membrane is 

 generally of a dull red color, with the veins dilated and varicosed. 



Give the causation. 



It is seen more frequently in old animals, and due to repeated 

 attacks of the acute form; it may be secondary to chronic lung dis- 

 eases, as emphysema, or in chronic heart troubles, where the blood 

 is backed up in the lungs, causing an irritation to the bronchial 

 mucous membrane. It is also seen in renal diseases. It may be 

 of specific origin. 



What are the symptoms? 



There is a distressing cough, with a thick or thin whitish 

 or yellowish-white expectoration, aggravated during changeable 

 weather. 



In old animals, suffering from heart disease or pulmonary 

 emphysema, there is an alteration of the respiration; the animal 

 puffs, especially on exertion, as the pulling of heavy loads or in 

 going up hill. As a rule, there is no rise of temperature, except, 

 possibly, a degree or two at the beginning or increase of the attack. 



Give the physical signs. 



The chest may be somewhat distended and the movements 

 limited. 



Percussion shows a clear or increased resonance. 



Auscultation shows the expiration somewhat prolonged and 

 wheezing; rales may be heard, varying in character, some being 

 high-pitched, others low, and some mucous rales. 



What is the prognosis ? 



It is hard to cure, as a rule, and can only be relieved. It is 

 apt to become exaggerated during changeable weather. 



Outline the treatment. 



This depends largely on the complications present; a change 

 of air is often beneficial where the attack is prolonged; in the city 

 send horses to the country. 



If there is excessive secretion, muriate of ammonia and senega, 

 or the iodide of potassium with nitric acid, is often good. 



