74 THEORY AND PRACTICE 



suming now that preceding the pneumonia there must be active 

 congestion of the lungs, the various stages are : 



1. Dry hot stage of inflammation in which 



the function is suspended. Walls of 

 the vesicles are dry, and during respi- 

 ration they crackle and the sound can 

 be heard by auscultation instead of 

 the normal respiratory murmur. 

 Stage lasts 6-10 hours. 



2. Stage of effusion — the lung becomes 



oedematous and will pit on pressure. 

 In the contagious pleuro-pneumonia 

 of cattle the cut lung will drip with 

 serum — never so oedematous in horses. 

 Stage lasts 3-4 days and gradually 

 drifts into the 3rd stage. 



3. Red hepatization — so-called because the 



lung resembles liver in consistency. 

 The third stage is long or short ac- 

 cording to the severity of it. Stage 

 lasts 1-2 weeks and drifts into the 

 fourth. 



4. Gray hepatization — 'this is practically 



the same as the 3rd stage except 

 that the tissue loses its color — the 

 hematin fades out. 

 The time of crisis comes at the height of the 3rd stage. 

 This is followed by a progressive softening which runs through 

 the 4th. In recovery the inflammatory deposits soften, liquefy 

 and become absorbed, terminating in resolution in the large ma- 

 jority of horses. More horses recover from pneumonia than 

 any other species of animal. It is marvelous to what extent 

 they recover. 



Pneumonia may occur in either one side or the other, either 

 the right or left lateral or both lungs, in which case it is double. 

 We find by experience that it occurs most often on the right 

 side. Right lateral pneumonia is more common than left lateral 

 or double. I think that in this respect it will correspond to the 



