Acute Pleurisy in the Horse, Pleuritis. 243 



for some time, the duliiess and absencs of sound will usually in- 

 dicate that the liquid rises to the same level on both sides. So 

 thin and permeable is the posterior mediastinum in its lower part 

 that unless thickly coated by new solid exudations, the effusion 

 readily passes through it and rises to the same height on both 

 sides. If gas as well as liquid is produced in the pleural sac a 

 gurgling or splashing sound may be heard on auscultation, and 

 occasionally, after rising or other change of position, a metallic 

 tinkling, due to droppings from the shreds of false membranes 

 above into the fluid below. 



As the disease proceeds dropsical effusions are observed beneath 

 the skin of the breast and abdomen, a mucous rattle is heard in 

 the trachea, the nose, ears and limbs become cold, the pulse in- 

 creases in rapidity and weakness, shows the distinct anaemic tremor 

 or thrill, and becomes rapidly imperceptible ; the horse moves un- 

 steadily and often falls suddenly dead. 



This early fatality is, however, only seen in the worst cases. 

 In those about to terminate favorably improvement is shown 

 usually about the fourth day. The lifting of the flanks and loins 

 becomes moderated, the ribs move more freely, the grunt ceases, 

 the pulse is fuller, softer and less frequent, and auscultation and 

 percussion show a steady decrease in the effusion. Appetite 

 meanwhile returns, the horse moves more freely, lies down for a 

 length of time in succession, and convalescence lasts from two to 

 three weeks. 



In the less fortunate cases structural changes more or less per- 

 manent, keep up symptoms of illness for a variable length of time. 

 Sometimes after the liquid effusion has been absorbed the lung 

 remains attached to the side of the chest by newly formed tissue 

 (false membrane) and while this is undergoing a drying and 

 organizing process, it gives rise to a leathery, creaking sound 

 heard on auscultation and easily mistaken for crepitation. Some- 

 times an abscess forms on the surface of the pleura or in the newly 

 organized false membrane, and either bursts "into the pleural sac 

 (empyema) where it serves to increase and sustain the irritation, 

 or it makes its way through the intercostal spaces and is discharged 

 externally. In this last case its advance toward the surface is 

 heralded by an extensive inflammatory infiltration and pasty 

 swelling much more tender to the touch than the dropsical swell- 



