29S CONTAGIOUS PLEURO-PNEUMONIA 



firm connective tissue which makes a crunching noise while 

 it is being cut with the knife. In other places we have 

 fatti' degeneration, caseation, calcification or suppuration, in 

 in which the enclosed lobules of the lungs, in consequence of 

 the existing suppuration become gangrenous, form sequestra 

 surrounded b}' sequestral cavities which have smooth walls. 

 The dead portions of the lungs may remain unchanged in these 

 cavities for a long time. Frequentlj' they become softened to 

 the consistency of a greasy, yeast-like paste. Sometimes, when 

 they are comparatively small, the}' become absorbed, and a scar 

 is lormed. The hepatized lobules of the lungs rarely' regain 

 their normal condition after the absorption of the exudate. 

 More frequenth' the}' atrophy or collapse, undergo atelectasis, 

 calcification or softening, become necrotic or suppurating or 

 form cavities. On the pleurae we find thick and wart-like 

 hypertrophies of conntctive tissue, which frequently cause the 

 lungs to adhere to the side of the chest. 



The changes in the lungs and pleurae are the most import- 

 ant general changes in cases of pleuro-pneumonia. It is 

 stated that we may sometimes meet with an interstitial fibrin- 

 ous exudate in the liver with atrophy of the liver cells ; sero- 

 fibrinous eft'usions into the articulations, tendon sheaths, sub- 

 cutis, dewlap and brisket ; intestinal catarrh ; areolation of 

 Peyer's patches anel ulcers on the gastro-intestinal mucous 

 membrane. 



The views of pathologists differ as to the nature of the 

 earliest changes in contagious pleuro-pneumonia and it is not 

 within the scope of this work to present imperfectly developed 

 or controverted theories. Without entering into a discussion 

 of the various views, it is clear that there is an inflammatory 

 condition of the connective tissue between the lobules, result- 

 ing in the exudation of coagulable lymph. This inflammation 

 is equally marked around tlie blood vessels and air tubes. It 

 leads to inflammatory changes in the inner wall ot the veins 

 and these cause a deposition of thrombi or plugs in the vessels, 

 which prevent the return of the blood. The blood pumped 

 into the lung tissue leaves the meshwork of capillaries around 

 the air vesicles, enters the latter and produces the firm hepa- 



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