G46 SPOEADIC DISEASES. 



caries and eburnation of the navicular bone, as results of acute 

 navicular arthritis succeeding an attack of rheumatic pleurisy. 



At the outset the inflammatory phenomena commence in the 

 subpleural tissue, the blood-vessels of which become congested. 

 At first the congestion presents an irregularly spotted appear- 

 ance ; the spots, however, multiply rapidly, and the red colour 

 becomes diffuse by their confluence. 



In other instances the pleural surface presents a streaky 

 appearance, whilst in others the whole of the pleura, pulmonalis 

 and costalis, presents a bright red congested appearance over its 

 surface. The secretion of the pleural surfaces is at first sus- 

 pended, and if the ear be applied to the side of this stage a dry 

 friction sound will be heard. 



The dryness of the membrane is very shortly succeeded by 

 effusion of serum, and the formation of an exudate which has a 

 tendency to become organized into a false membrane, causing 

 the adhesion of the two pleural surfaces. 



It is important that the time in which these false membranes 

 may be formed be clearly ascertained. The experiments of 

 Andral throw some light upon this subject, which is important 

 to the veterinarian as a question of jurisprudence. 



Andral made experiments upon the pleura of rabbits by 

 injecting acetic acid into them. 



He sometimes found at tlie end of nineteen hours soft, thin, 

 false membranes, traversed by numerous anastomosing red lines. 



In other rabbits, placed under circumstances which appear to 

 be exactly similar, no such result had taken place at the end of 

 a much longer period ; and the pleura contained only a serous 

 or puriform liquid, mixed with unorganized flakes of lymph. 



Experiments performed by myself upon healthy subjects 

 (horses) in 1874 proved that a false membrane, presenting some 

 degree of organization, may be found in twenty-four hours after 

 the injection of an irritant into the pleural sac, and that the 

 puriform appearance mentioned by Andral is an evidence of an 

 inflammation of longer standing, arising from degeneration of the 

 inflammatory products. 



It may be briefly stated that all cases of pleuritis terminate 

 either in the exudation of lymph, which may liquefy and be 

 re-absorbed, or in the formation of a permanent false mem- 

 brane. But the most ordinary result is effusion of serum, 

 constituting a limited hydrothorax, even to invasion of the 



