Anatomical Changes. 537 



terior lobes) or tubercles of all sizes may be scattered through 

 the entire substance of the lung. 



The confluence of cheesy or caseo-purulent foci of all sizes 

 leads to the formation of cavities which are surrounded by 

 dense connective tissue lined on the inside with suppurating 

 granulation tissue which was formerly called the pyogenic 

 membrane. The interior of these cavities contains strands 

 of connective tissue which are obliterated blood vessels. Some 

 of these cavities communicate with bronchial tubes through 

 which they discharge their contents to the outer world. As 

 a result of exposure to the air the muco-caseous material which 

 is retained in these open cavities decomposes into discolored 

 ill-smelling masses (phthisis tuberculosa). 



In young animals pulmonary tuberculosis frequently occurs 

 exclusively in the form of catarrhal pneumonia. The diseased 

 parts of the organ appear uniformly firm, solid and devoid of 

 air. The cut surface is reddish-gray, grayish-white or yellowish- 

 gray and presents to view a slight quantity of cheesy matter 

 that can be scraped off with a knife. Here too the cheesy 

 degeneration of the exudate and the breaking down of the lung 

 tissue results in the formation of dry or soft cheesy foci of 

 various sizes. Tuberculosis of the superficial layers of the 

 pulmonary tissue is frequently attended with a productive in- 

 flammation of the pleura. This may lead to pleural adhesions 

 or to the development of excresences which will be described 

 below. In rare cases a sero-fibrinous pleuritis develops. 



Besides the affection of the lung tissue proper there is 

 a catarrhal condition in the bronchial tubes of the diseased 

 areas. In severe cases all of the bronchial tubes may be filled 

 with muco-purulent secretions. The mucous membranes are 

 swollen and injected and frequently contain tubercles and 

 ulcers ; they may become detached from the bronchial walls and 

 obliterate the lumen or cause bronchiectases. Ulceration of 

 the bronchial mucous membrane is not infrequent. The tuber- 

 culous nature of the ulcers is indicated by their irregular form, 

 raised borders and yellowish-red base, and by the fact that 

 on and around the ulcers there are small tul)ercles to be seen. 

 Sometimes dense masses of tuberculous growths are found in 

 the larynx, especially in the ventral angle of the glottis. They 

 may completely cover the vocal chords or be fused into one 

 large tumor. In exceptional cases the nasal mucous membrane 

 may be covered with yellowish-red granulations containing 

 numerous caseous foci (Joest). 



Tuberculosis of the serous membranes is characterized in 

 the beginning by grayish-red, succulent, soft, yet tough ex- 

 cresences in some of which yellowish nodules may be found. 

 In the later stages there are firm dense globular formations 

 (pearl nodes) with cheesy or mortar-like foci in their interior. 

 The smaller excresences may be attached by means of a broad 

 base or may be pedunculated. They frequently become ad- 



