132 DISEASES OF THE HOBSB. 



chest and other contiguous parts which come in contact. It must be 

 remembered that the lungs are dilating each time a breath is taken 

 in, and contracting each time a breath of air is expelled. It may be 

 readily seen that if it were not for the moistened state of the surface 

 of the pleura the continual dilatation and contraction and the conse- 

 quent rubbing of the parts against each other would cause serious 

 friction. 



Inflammation of this membrane is called pleurisy. Being so closely 

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

 disease 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, confinement 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, 

 confined 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 membrane 

 is the primary seat of the disease. It may occur in conjunction with 

 bronchitis, influenza, and other diseases. Diseased growths that 

 interfere with the pleura may induce pleurisy. The most frequent 

 cause of pleurisy is an extension of inflammation from adjacent dis- 

 eased lung. It is a common complication of pneumonia. Pleurisy 

 will be described here as an independent affection, although it shoiild 

 be remembered that it is very often associated with the foregoing 

 diseases. 



The first lesion of pleurisy is overfilling of the blood vessels that 

 ramify in this membrane, and dryness of the surface. This is fol- 

 lowed by the formation of a coating of coagulated fibrin on the 

 diseased pleura and the transudation of serum which collects in tTie 

 chest. This serum may contain flakes of fibrin and it may be straw 

 colored or red from an admixture of blood. The quantity of this 

 accumulation may amount to several gallons. 



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 rib's are fixed, that is, the ribs move very little in the 

 act of breathing, 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 down, but does not remain long down, for when he 

 finds no relief he soon gets up. After effusion begins these signs of 

 Digitized by Microsoft® 



