MORBID ANATOMY 297 



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, be- 

 cause they are the oldest, are usually in the stage of yellow 

 or gray hepatization. Some of the inclosed lobules of the 

 lungs are normal or only compressed, while others are merely 

 hyperaemic. If we closely examine the bright interstitial 

 lines, we find that thej^ consist at first of an oedematous 

 infiltration, which, later on, becomes plastofibrinous, gelat- 

 inous, indurated and finally tends to the formation of ad- 

 ventitious 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 consti- 

 tution. 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 

 infiltrated with cells and their lumen is in a state of throm- 

 bosis. The blood-vessels frequently show thrombi and small 

 hemorrhagic infarcts. The contents of the finer bronchi are 

 often infiltrated with numerous white corpuscles. The bron- 

 chial glands and frequently the mediastinal glands are in- 

 flamed and swollen. 



The pleurae are covered with soft, membranous, fibrinous 

 masses, which are sometimes lumpy or crumbling 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 containing 

 ecchymoses and the surface of the pleurae in a rough and 

 uneven condition. In the thoracic cavity we find, in varying 

 quantity, a generally inodorous fluid exudate, which may be 

 clear or opaque and which contains flakes or lumpy masses. 

 Similar fibrinous masses often lie on the outer surface of the 

 pericardium. 



After the disease has existed for some time, the affected 

 parts of the lungs undergo induration, cicatrization, caseation, 

 calcification, necrosis or suppuration. At first the interstitial 

 infiltration becomes dense, solid and dry and changes into 



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