352 DISEASES OF THE RESPIRATORY ORGANS. 



cavities with cheesy walls, resulting from the breaking down 

 and evacuation of the caseous material. The pleura is gener- 

 ally thickened, especially over the apices. 



Microscopically it is noted that the areas of consolidation 

 are formed of the smaller patches just described, each with a 

 caseous centre and an outer zone of air-spaces filled by inflam- 

 matory exudations. The peribronchial connective tissue and 

 alveolar septa are infiltrated as in lobular pneumonia, and 

 occasionally typical histological tubercles may be seen here 

 and there, especially at the periphery of the pneumonic areas. 



FIG. 156. 



Section of lung from a case of acute phthisis, showing that the consolidation con- 

 sists almost exclusively of products accumulated within the alveoli. In some 

 parls a free space is seen between the alveolar walls and their contents; this 

 is due simply to the shrinking of the latter caused by hardening of the speci- 

 men. X 50 (Green). 



Besides the cases whicli conform to a lobular type of pneu- 

 monia, others have been described which resembled lobar 

 pneumonia, not only in the character of the inflammatory 

 exudate, but also in its lobar distribution. In some instances 

 of acute phthisis, tubercles may be entirely absent, or at least 

 indistinguishable in consequence of the extensive caseous de- 

 generation ; though they can generally be found, if not in the 

 lungs, on the pleura, or peritoneum, or elsewhere. 



