THE RESPIRATORY SYSTEM 93 



which fact is of diagnostic value. The course of septic 

 pneumonia is uncertain. The attack may terminate 

 fatally in two or three days after the onset of the disease 

 or, if the septic lesions are limited in extent, they may 

 become encapsulated and the animal recover, the length 

 of time required varying from a few weeks to as many 

 months. 



Treatment. Remedial agents are of little, or no 

 value so far as the septic process is concerned. The 

 treatment of symptoms as they develop will be of some 

 value. The animal should be given good care and 

 sanitary surroundings provided. 



Interstitial or Chronic Pneumonia 



Interstitial pneumonia is a chronic condition char- 

 acterized by proliferation of fibrous tissues. This con- 

 dition is usually a sequel to chronic catarrhal bronchitis 

 and chronic bronchopneumonia. It is observed in swine 

 in those sections of the country where it is continuously 

 dusty and in swine kept in quarters where slightly irri- 

 tating gases prevail. 



Etiology. Constant inhalation of mild irritants, such 

 as dust or chemical fumes. 



Lesions. Fibrous proliferation characterizes this 

 disease. The fibrous tissue forms around the bronchioles, 

 the process gradually extending and involving the alveoli. 

 The bronchioles and alveoli also show evidence of catarrh. 

 The affected lung is dense, and when cut offers more 

 resistance than the normal lung. The degree of fibrous 

 proliferation is quite variable in some instances; there is 

 a limited amount, and in other cases the normal lung 

 tissue is displaced by fibrous tissue. Encapsulated 

 suppurative or necrotic centers may be found. 



Symptoms. A persistent cough, associated with a 

 limited but variable nasal discharge of a mucopurulent 

 material, characterizes chronic pneumonia. The animals 

 are usually unthrifty and emaciated. 



Treatment. The cause should be removed and the 

 animals properly housed and fed. Other than this, little 

 can be done. 



