LOB AM PNEUMONIA. 



341 



walls. The exudate in the bronchioles and on the pleural 

 surface is composed of similar elements. The capillary blood- 

 vessels of the delicate walls of the air-spaces are much less 



FJG. 150. 



Section from lung in the second or exudative stage of croupous pneumonia, a, en- 

 dothelial wall of a small vein : 6, blood within the vein, unusually rich in leu- 

 kocytes, which have collected during the slowing of the circulation. The line 

 6 points to the nucleus of a leukocyte. Part of the blood has fallen out of the 

 section during its preparation, c, leukocytes beneath the endothelium of the 

 vascular wall; d, oedematous fibrous tissue surrounding the vessel. The fibres 

 of the tissue have been separated by the exuded serum. This tissue is also 

 moderately infiltrated with leukocytes that may have passed through the walls 

 of the vein, and contains a few red blood-corpuscles, e, wall separating two 

 pulmonary alveoli. This is also somewhat infiltrated with leukocytes. /, exu- 

 date within an alveolus, consisting of serum, fibrin, leukocytes, and red blood- 

 corpuscles ; it also contains a few epithelial cells desquamated from the alveolar 

 wall, g. 



prominent than in the first stage, but are surrounded by 

 migrated leukocytes and proliferating connective-tissue cells, 

 forerunners of the hyperplasia of connective-tissue which 

 occurs in some chronic pneumonic processes (see Figs. 150 

 and 151). 



In the stage of gray hepatization the lung- tissue still re- 

 mains solid, but becomes mottled in appearance, and finally 

 a uniform gray in color. 



Microscopically it is found that the red blood corpuscles 

 have become decolorized or have disappeared, and the fibrin 

 filaments are broken down and granular. The exudate does 



