100 THE PLEURA ADHESION: [BOOK U 



enters that is to inflate them. At the same place 

 is fastened the ends of a thin membrane, or rather 

 two membranes, that enclose each one of the lobes : 

 this membrane is termed the pleura, and seems de- 

 signed to admit of one lobe performing its functions 

 whenever the other may, at any time, be diseased. 

 Between the two lobes the pleura is double, and, 

 from its situation in the middle (in medio) is called 

 mediastinum : it forms a passage for the great blood- 

 vessels running near the spine, and is very liable to 

 contract cold, which shows itself in " thick wind" 

 or rather short wind. See sect. 36. In the pleura, 

 then, are wrapped up, as in two silk handkerchiefs, 

 the two lobes of the lungs, the upper part of that 

 membrane being fastened to the spine and ribs ; and 

 on its surface is generated or secreted some of that 

 oily fluid we before spoke of (sect. 20, 21), which 

 is designed to keep the parts moist, and prevent 

 their adhering together. His powers of secretion, 

 however, and those of this organ in particular, often 

 fail in the horse, in consequence of his very great 

 exertions, combined with the heat of his blood, ex- 

 hausting more than the secretory power can supply ; 

 and we frequently find the pleura growing to the 

 ribs, the lungs, or the midriff, by reason of its 

 wanting a due portion of this oily fluid ; from the 

 same cause (a defect in the secretion), we sometimes 

 find the upper surface of the stomach partially at- 

 tached to the midriff, evidently caused by inflamma- 

 tion of the parts. But whichever of those misfor- 

 tunes attend the horse, he is invariably " hurt in 



