154 RUPTUEE OF THE DUPHRAGM THE rLEXTRA 



RUPTURE OF THE DIAPHRAGM. 



This may sometimes occur from any extraordinary exertion, 

 particularly when tke stomach is distended with food or gas. 



In mpture of the diaphragm, the horse usually sits or his 

 haunches, like a dog ; but this is far from being an infallible 

 symptom of the disease. It accompanies introsusception, as well 

 as rupture of the diaphragm. [Mr. Youatt gives no remedy, and 

 probably the case admits of none ] 



THE PLEURA. 



The walls of the chest are lined, and the lungs are covered, by 

 a smooth glistening membrane, the pleura. It is a serous mem- 

 brane, so called from the nature of its exhalation, in distinction 

 from the mucous secretion yielded by the membrane of the air- 

 passages. The serous membrane generally invests the most im- 

 portant organs, and always those that are essentially connected 

 with life ; while the mucous membrane lines the interior of the 

 greater part of them. The pleura is the investing membrane of 

 the lungs, and a mucous membrane the lining one of the bronchial 

 tubes. 



Among the circumstances principally to be noticed, with regard 

 to the pleura, is the polish of its external surface. The glistening 

 appearance of the lungs, and of the inside of the chest, is to be 

 attributed to the membrane by which they are covered, and by 

 means of which the motion of the various organs is freer and less 

 dangerous. Although the lung^, and the bony walls which con- 

 tain them, are in constant approximation with each other, both 

 in expiration and inspiration, yet in the frequently hurried and 

 violent motion of the animal, and, in fact, in every act of expi- 

 ration and inspiration, of dilatation and contraction, much and 

 injurious friction would ensue if the surfaces did not glide freely 

 over each other by means of the peculiar polish of this membrane. 



Every serous membrane has innumerable exhalent vessels upon 

 its surface, from which a considerable quantity of fluid is poured 

 out. In life and during health it exists in the chest only as a 

 kind of dew, just sufficient to lubricate the surfaces. The pleura 

 possesses very little sensibility in health, but it is otherwise when 

 it is the seat of disease. In pleurisy, pneumonia, &c., it becomes 

 susceptible of intense pain. 



The pleura adheres intimately to the ribs and to the substance 

 of the lungs. While the diseases of mucous membranes spread 

 to other parts, those of serous membranes are generally isolated. 



