82 THEORY AND PRACTICE 



an animal has a long wet coat and stands for some time, he may 

 come down with an attack of pleurisy in a few hours. 



Blood Contamination. — The so-called ''sale stable fever" or 

 influenza, may cause pleurisy, but it is general while that due 

 to the other three causes is localized. 



Pleurisy may develop from intrinsic conditions within the 

 body, as from anaemia or pyaemia. Hereditary conditions, acute 

 rheumatism or typhoid fever may cause it. It may be incidental 

 to old age. In these latter conditions the pleurisy develops as a 

 complication. 



Course. — Pleurisy runs through four well-defined stages: 



1. Stage of active congestion. 



2. Dry hot stage of inflammation (first) 



3. Oedematous stage of inflammation 



(second). 



4. Absorption (if horse does not die). 



Special Pathology. — In the fi'rst stage of pleurisy, the pleura 

 becomes congested in streaks, spots or patches. These by ex- 

 tension become confluent until the whole pleural surface is bright 

 red. This condition is accompanied by definite symptoms on the 

 part of the animal. These symptoms are very marked and they 

 do not occur in the congestive stage of any other inflammation. 

 The second stage of pleurisy (the first or dry hot stage of in- 

 flammation) is characterized by a dry hot pleural membrane 

 whose function is suspended. The costal and pulmonary pleura 

 are both dry rubbing on each other, and by auscultation friction 

 sounds can be detected. The second stage is short, 6-8 hours. 

 The third stage is the second or oedematous one of inflammation 

 and is divided into two parts: A plastic exudation upon the 

 pleural surface (the pleura is so dense that it cannot easily be- 

 come infiltrated), — a coagulated mass forming a false mem- 

 brane. In this first part of the third stage pleurisy may termi- 

 nate by resolution, a sort of fatty degeneration of the false mem- 

 brane; or if both pleurae are involved, they may adhere and 

 grow together, forming a perfect adhesion, common in cattle and 

 in people, but not often in horses. Recovery may take place 

 after adhesions have formed, but the adhesions remain perma- 

 nent. The second half of the third stage is characterized by an 



