130 DISEASES OF THE RESPIRATORY ORGANS. 



chronic, and a progressive atrophy of the alveolar walls takes place 

 until they are entirely closed up, the neighboring alveoli become 

 absorbed or altered, and finally cavities are formed, and the blood- 

 vessels become atrophied. On section of the lung the edges of the 

 cavities are pale, soft, and the bloodvessels are stained with pig- 

 ment. Sometimes laceration of the alveolar walls allows air to 

 penetrate into the interlobular, interstitial, or subpleural connective 

 tissue; this is generally caused as a result of severe and continual 

 coughing spells, and where animals have died from some form of 

 suffocation. Siedamgrotzky describes a case where an old emphy- 

 sematous dog had a severe fit of coughing and the lung was lacer- 

 ated, causing pneumothorax. 



DISEASES OF THE PLEURA. 



Inflammation of the Pleura ; Pleurisy. 

 (^PleurUis.) 



Etiology. The disease is divided into two forms — primary 

 and secondary pleuritis. The primary form may be caused by 

 cold, from traumatism, etc. ; the secondary from the extension of 

 inflammations from the surrounding organs, as in pneumonia, gan- 

 grenous pericarditis, peritonitis extending through the diaphragm, 

 fractured ribs, injuries to the walls of the thorax, or perforation 

 of the throat by foreign bodies. We also see it in all forms of 

 pysemia and tuberculosis. 



Pathological Anatomy. The pleura is dull and swollen 

 and very much injected, rough ou the surface, due to it being cov- 

 ered with fibrinous accumulations (small button-like elevations), 

 and in the advanced stages large masses of fibriuous substances. 

 When there is no accumulation of fluids it is called pleuritis 

 fibrinosa. But generally we find a more or less copious secretion 

 of fluid from the capillaries. This fluid (pleuritic exudation) 

 accumulates between the pleural folds in copious fibrinous masses; 

 it is usually serous or sero-fibrinous, appearing as a slightly yel- 

 lowish turbid fluid, with more or less fibrinous coagula swimming 

 in it. Chemically it is almost like blood-serum. This liquid 

 contains red blood-corpuscles and round cells; if the former is in 

 large numbers, the hemorrhagic exudation is found; but if the cells 



