48 DISEASES OF SWINE 



become chronic if the irritation is kept up. In such 

 cases unthriftiness is a prominent symptom. 



The above symptoms are not seen in all cases 

 of pneumonia. In bronchial and lung worm dis- 

 eases, a small part of the lung tissue may be in- 

 volved, and the symptoms resemble these diseases 

 more than they do pneumonia. 



Lesions.^ — The character of the lesions differ in 

 the different cases. If death occurs within a few 

 days after coming down with the disease, a large 

 part of the lungs may appear solid and liver-like 

 in color and consistency (hepatization). Later a 

 part becomes lighter in color (gray hepatization). 

 This marks the beginning of the degenerative 

 changes of the inflammatory exudates and the re- 

 turn to the normal. On cutting into the tissue that 

 has reached this stage, a purulent or fatty-looking 

 fluid may exude from the cut surface. A part may 

 have reached a later stage, that of resolution, and 

 the absorption of the inflammatory exudates begun. 

 Suppurative changes in the lung tissue may also 

 occur. 



In lobular pneumonia the lesions vary more than 

 in the form just described. The bronchial tubes 

 may be plugged with mucus and inflammatory ex- 

 udates, and the lining membrane inflamed. Small 

 areas of lung tissue undergoing different stages of in- 

 flammation are seen scattered through the lung, 

 with here and there dark colored, depressed por- 

 tions in which the air cells have collapsed (atelec- 

 tasis). Some lobules may appear bulging and 



