DISEASES OF THE RESPIRATORY SYSTEM. 149 



Tlie stage of effusion is characterized by the pouring out of 

 a semi-fibrinous liquid; more or less filling the cavity and floating 

 in this fluid are flocculi of fibrine, blood, and epithelial cells. 



The exudation is called serous, fibrinous, or fibrino-serous. 



In the third stage this material may undergo fatty degeneration 

 and become absorbed, in which case resolution takes place; or, on 

 the other hand, it may become organized and form false membranes. 

 In the human subject we often find the lungs attached to the walls 

 of the thoracic cavity, in which case it becomes^ necessary to cut 

 these adhesions to remove the lungs; this is rarely found in the 

 equine, but is quite common in the dog. 



The serous part of the exudation may become absorbed by 

 the blood-vessels and the lymphatics; the character of the inflam- 

 mation we generally see in the horse is the subacute form, which 

 contains more serum than fibrine, and therefore so dangerous on 

 account of drowning out the lungs, as we say, and the animal dies 

 from exhaustion. 



Is this a unilateral or a bilateral disease ? 



This is somewhat of a disputed point. 



On post-mortem examination we find the fluid in both cavities. 

 This is claimed to be a peculiarity — that is, there is a connection 

 between the two pleural cavities — a perforation of the mediastinal 

 pleura. 



Some say that this perforation is made after death. 



There are, no doubt, openings between the two pleural cavities, 

 and thus it is termed a bilateral disease, although, primarily, one 

 pleura only may be affected. As the effusion is thrown out it ac- 

 cumulates in both lungs, and thus the bilateral physical signs. 



What are the symptoms? 



At times the symptoms are vague, and, while treating laryn- 

 gitis and the like, this disease may be developing and we may over- 

 look it. It very often is associated with or follows pneumonia. 



In other cases the symptoms are striking; it commences with 

 a chill, the animal becoming dull, the hair roughened, muscular 

 tremblings, coldness of the extremities and skin, followed by febrile 

 symptoms; the hair falls down, the body becomes warm, and the 

 mucous membrane injected. 



The pulse in pleurisy is small, quick, and hard — a so-called 

 wiry pulse, which is characteristic of inflammations of serous mem- 

 brane: later it becomes softer and weaker. 



