434 CHRONIC INFECTIOUS DISEASES 



whereby it grits under the knife when cut through. Usually 

 in the neighborhood of a larger node, small tubercles are pres- 

 ent. WhUe the lung tissue between the tubercles is often 

 normal, sometimes the intervening alveoli are filled with 

 tubercular exudate and the interstitial tissue thickened. By 

 the confluence of smaller nodes great tubercular masses form. 

 Sometimes the center. of the mass is hollow (caverns), but 

 more often filled with friable, dry caseation or moist pus. 

 Between some of the cavities and bronchi a communication 

 forms through which a secondary infection with pus cocci or 

 saprophytic bacteria takes place, in some instances changing 

 the character of the caseous or puriform mass to that of 

 ichor, causing the color to become grayish and giving it a 

 fetid odor. Tuberculosis of the superficial parts of the lung 

 often extends to the pleura, leading usually to circumscribed, 

 pleuritic adhesions . Very rarely a diffuse, serofibrinous pleuritis 

 develops. 



In calves pulmonary tuberculosis assumes the form of a 

 catarrhal pnemnonia. On cut surface the affected area of 

 the lung is strewn with small, round, reddish-gray to yellow 

 areas, which, by confluence, are enlarged to caseous centers 

 the size of a hickory nut or larger. Bronchitis almost always 

 attends pulmonary tuberculosis, therefore lesions in the 

 bronchi are noted on postmortem. The signs of bronchial 

 catarrh with bronchiectasis are common findings, the dilated 

 air tubes filled with mucus or cheesy masses. At times the 

 bronchial mucous membrane is ulcerous. The trachea is less 

 liable to ulceration than the larynx. In the latter organ 

 tumor-like, connective-tissue growths occur, sometim'es almost 

 entirely occluding the lumen. On section the neoplasm is 

 found to contain small, gray or yellowish tubercles. 



Serous Membrane. — ^The pleura is most frequently involved. 

 In the earliest stages reddish-gray, small granules develop 

 surrounded by masses of connective tissue. On section of 

 these masses areas of caseation from a millet seed to a pea in 

 size are revealed. By confluence and simultaneous connective- 

 tissue proliferation, round nodes or cauliflower-like excres- 

 cences protrude from the serous membrane. The protuber- 

 ances may have a broad base or be pediculated. While in 



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