THE EESPIRATORY SYSTEM 89 



Proper sanitary conditions should be provided, and the 

 affected animals should be given easily digested, whole- 

 some food in sufficient quantities to build up the body 

 and maintain strength. If the causative factor is an 

 infection, isolation and proper quarantine regulations 

 should be enforced. 



Croupous Pneumonia 



Croupous pneumonia is a disease involving lobes or 

 large lung areas and is characterized by the presence of 

 a hemorrhagic exudate in the air cells. It is not a common 

 primary condition in swine, but is frequently associated 

 with hog cholera. 



Etiology. Many predisposing factors enter into the 

 causation of this disease, such as undue exposure or 

 inhalation of irritating gases, but it is probable that the 

 specific active cause is microbian. 



Lesions. Croupous pneumonia is characterized by 

 the regularity of the successive changes that occur in the 

 affected portion of the lung. The disease usually involves 

 the dependent part of the lung and is essentially lobar, 

 but more or less than this amount of lung may be involved. 

 The various stages \that occur in the lung are as follows: 

 congestion, red hepatization, gray hepatization, and 

 resolution. These stages occur in the order mentioned, 

 and there is no distinct line of demarcation between 

 each succeeding stage. The length of duration of each 

 stage is subject to variation, but on the whole is quite 

 constant. The congestive stage is of about twenty -four 

 hours* duration. During this stage the affected portion 

 of the lung is engorged with blood. In the beginning 

 the air cells contain air but as the disease progresses 

 the alveolar capillaries begin to leak or there is a hemor- 

 rhagic exudate into the alveoli. Red hepatization begins 

 when exudation is evident, and this stage persists for 

 from three to five days; the area affected is red, dense, 

 heavy, and liver-like. Gray hepatization is characterized 

 by a gray or yellow coloration of the affected lung. This 

 stage succeeds red hepatization and is due in part to the 



