INFLAMMATION OF THE PLEURA. 265 



The case is different in the pleurisy which sometimes accompanies 

 septicaemia, puerperal fever, scarlet fever, a'nd other infectious dis- 

 orders. Such a pleurisy arises independently of the action of any new 

 irritant, and forms one of the nutritive derangements which proceed 

 from infection of the organism by putrid matter, scarlatinous poison, or 

 the like. This secondary pleurisy, which generally produces a pura- 

 loid exudation full of young cells, is attended by inflammation of other 

 erous membranes. 



The exciting causes of pleurisy are 



1. Injuries of the ribs and pleura, and the entrance into the latter 

 of foreign bodies, such as pus, blood, air, and the contents of cavities. 

 Such exciting causes generally give rise to a form of pleurisy, accom 

 panied by a very profuse sero-fibrinous exudation into the pleural sac. 



2. Pleuritis often arises through propagation of inflammation from 

 neighboring organs, as from the lungs to the substance of the pleura. 

 In these cases the exudation generally is scanty and fibrinous, although 

 it sometimes is very copious and sero-fibrinous. 



3. Next in order come the very numerous instances in which pleu- 

 risy is caused by the advance to the pleura of neoplasms, especially of 

 tubercle and carcinoma. Here the pleurisy is dry, or else it results in 

 adhesions of the opposing surfaces of the pleura, or else a more or less 

 plentiful effusion into the sac may form, or, finally, tubercle or cancer 

 may develop in the pseudo-membrane. 



4. Pleurisy is often the consequence of exposure to cold, or to the 

 action of other atmospheric or telluric influences, of which we have no 

 definite knowledge. In this form, which is an independent, idiopathio 

 disease, and which is usually called rheumatic pleurisy, there is a 

 great deal of variety as to the quantity and character of the effusion. 



ANATOMICAL APPEARANCES. In commencing pleuritis, the pleura 

 is reddened by injection proceeding from the sub-serous Connective 

 tissue, and producing fine rose-red points and stripes upon its surface 

 Besides this distention of the capillaries, we often find slight extrava- 

 sations of blood, ecchymoses, forming irregular dark spots, in which 

 the ramifications of small vessels are visible. The tissue of the pleura 

 is infiltrated, the epithelium is nearly all cast off, the surface, formerly 

 smooth and glossy, looks dull, the pleura itself is somewhat swollen. 1 

 Gradually the free surface begins to assume a rough, shaggy appear 

 ance. This is due to the development of minute delicate folds, and 

 papillary granulations, which are firmly attached to the surface, and 

 are not to be confounded with fibrinous deposits. Microscopically, 

 these granulations consist of newly-formed fusiform cells, and tender 

 filaments of wavy connective tissue, with considerably-elongated capil- 

 laries, which are coiled into loops within them (Foerster). 



