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and contraction and the consequent riiboing of the parts against each 

 other would cause a serious friction. This, then, is the office of the 

 l^leura— to secrete or moisten its surface with a fluid to prevent the ill 

 effects of friction. 



Inflammation of this membrane is called pleurisy. Being so closely- 

 united with the lung, it can not always escape participation in the dis- 

 ease when the latter is inflamed. Pleurisy may be due to the same 

 predisposing and exciting causes as mentioned in the beginning of this 

 work as general causes for diseases of the organs of respiration, such 

 as exposure to sudden changes of temperature, couflnement in damp 

 stables, etc. It may be caused by wounds that penetrate the chest, for 

 it must be remembered that such wounds must necessarily pierce the 

 pleura. A fractured rib may involve the pleura. The inflammation 

 following such wounds may be circumscribed, that is, coufiued to a 

 small area surrounding the wound, or it may spread from the wound 

 and involve a large portion of the pleura. The pleura may be involved 

 secondarily when the heart or its meuibrane is the primary seat of the 

 disease. It may occur in conjunction with bronchitis, influenza, and 

 other diseases. It is commonly seen in connection with rheumatism. 

 Diseased growths that interfere with the pleura may induce pleurisy, 

 but it is most frequently met with in connection with pneumonia, for 

 the reason given heretofore. Pleurisy will be described here as an 

 independent afi'ection, although it should be remembered that it is very 

 often associated with the foregoing diseases. 



When the animal is affected with pleurisy an ordinary observer should 

 have no difficulty in detecting the disease, provided the diagnostic 

 symptoms are studied beforehand. The very first stage is a congested 

 state of the blood vessels in the parts affected; the surface of the mem- 

 brane becomes dry and roughened (this fact will be again referred to 

 when the symptoms are described). This dry condition is followed, after 

 a certain period, by an effusion of fluid, that is, more fluid than usual is 

 thrown off" by the membrane when in a diseased condition. This fluid 

 accumulates in the space between the lungs and the walls of the chest, 

 constituting hydro-thorax, or dropsy of the chest. This fluid may 

 undergo certain changes; in it float coagulated masses called fibrin. 

 The surface of the lung may adhere to the internal surface of the ribs. 

 The quantity of exuded fluid varies to a great extent. In some cases 

 the chest contains an enormous amount, and when it is not absorbed 

 pus may be generated to a greater or less extent. 



Symptoms. — When the disease exists as an independent affection it is 

 ushered in by a chill, but this is usually overlooked. About the first 

 thing noticed is the disinclination of the animal to move or turn round. 

 When made to do so he grunts or groans with pain. He stands stiff; 

 the ribs are fixed, that is, the ribs move very little in the act of breath- 

 ing, but the abdomen works more than natural; both the fore feet and 

 elbows may be turned out; during the onset of the attack the animal 

 may be restless, and act as if he had a slight colic; he may even lie 



