448 CONTAGIOUS PLEURO-PNBUMONIA 



var}' in color from orange to dirty white and which surround 

 the dark colored lobules of the lung. The larger lobules 

 have a thickness of from .2 to 5 cm. ; and the smaller ones of 

 from .25 to .50 cm. The color of the enclosed lobules of the 

 lungs depends on the duration of the process and varies from 

 brown-red to dirty yellow. The recently infected lobules have 

 a blood-red, reddish-brown or dark brown color (stage of red 

 hepatization). The color of the older ones varies from orange 

 to yellow (yellow hepatization) and that of a still older date is 

 gray (gray hepatization). The central foci, because they are 

 the oldest, are usually in a stage of yellow or gray hepatization. 

 Some of the enclosed lobules of the lungs are normal or only 

 compressed, while others are merely hyperemic. If we closely 

 examine the bright interstitial lines, we find that they consist 

 at first of an edematous infiltration, which later on becomes 

 plastofibrinous, gelatinous, indurated and finally tends to the 

 formation of adventitious connective tissue. The lymph-spaces 

 in the lines are dilated like lacunae and filled with a serous or 

 fibrinous fluid. In robust animals, the exudate in the alveoli 

 is firm ; but is of a more serous character in animals of a weak 

 constitution. In the former case, a section made through the 

 lung will be found to be granular. Besides these changes, the 

 other lymph vessels of the lungs are dilated, their walls are in- 

 filtrated with cells and their lumen is in a state of thrombosis. 

 The blood vessels frequently show thrombi and small hemor- 

 rhagic infarcts. The contents of the finer bronchi are often 

 infiltrated with numerous white corpuscles. The bronchial 

 glands and frequently the mediastinal glands are inflamed and 

 swollen. 



The pleurae are covered with soft, membranous, fibrinous 

 masses, which are sometimes lumpy or crumbled and which 

 can easily be detached. These deposits have a reticular sur- 

 face and may attain a thickness of 2 cm. If we remove them, 

 we shall find the pleural vessels highly injected with ecchy- 

 moses, and the surface of the pleurae in a rough and uneven 

 condition. In the thoracic cavity we generally find, in vary- 

 ing quantity, an inodorous fluid exudate, which may be clear 



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