336 TUBERCULOSIS 



Caseous Infiltration. When many tubercles in the same area 

 undergo caseation, and when these caseous masses become more or 

 less confluent and form one larger territory, the process is termed 

 caseous infiltration of a part or organ. This ^ form of caseous infil- 

 tration can best be seen in the lungs of cattle before cavity formation 

 has occurred and in the lymph glands. The tissues of these structures 

 become infiltrated by a rather dry, elastic, cheesy material, generally 

 grayish white or light grayish in man, and more decidedly yellowish 

 (like the boiled yolk of an egg) in cattle. In the latter these caseous 

 infiltrations may lead to the formation of masses of several pounds' 

 weight. When they have attained such a large size they are frequently 

 riddled with areas where the caseous material has been softened and 

 even completely liquefied. 



Cold Abscess and Cavity Formation. When the caseation and 

 liquefaction of neighboring tubercles lead to the formation of a 

 larger abscess filled with more or less liquefied material which 

 may be discharged through an open ulcer or a fistulous tract the 

 process is known as a tubercular or a cold abscess. Such an abscess is 

 generally surrounded by a wall, on the inner free surface of which 

 may be seen miliary and submiliary tubercles. When these abscesses 

 have been formed in the lungs and have discharged part of their 

 fluid contents they are known as pulmonary cavities, or caverns. 

 They generally break by ulceration or the formation of a fistulous 

 tract into a bronchus, and discharge their contents by coughing. 

 Such cavities, as an invariable rule, sooner or later become infected 

 from the outside by other microorganisms (staphylococci, streptococci, 

 Bacillus pyocyaneus, etc.). This process is known as a mixed tuber- 

 cular infection. Tubercular lesions of the intestines, after they have 

 ulcerated, generally become infected with the colon bacillus. In 

 tuberculosis, abscess formation occurs not only in soft tissues, but it 

 may also take place in the bones. Here the tubercular abscess or 

 cavity generally contains bone fragments or bone sand, and also 

 occasionally complete sequestra floating in the softened tubercular 

 material; sometimes the area where the bone has been broken down 

 and carried away is filled with a fungous tubercular granulation 

 tissue. 



Tubercular Ulcers. Tubercular ulcers are frequently found in the 

 intestines, the larynx, trachea, and bronchi as a result of tubercles 

 or confluent tubercles which have first undergone caseation in the 

 centre, the necrotic process having broken through the outer surface 

 and having led to the formation of open sores. The latter are 

 generally circular or oval, with a ragged, irregular base, grayish-red 

 or yellowish, mottled, often studded with tubercles which surround 

 them at the margin. 



Miliary Tuberculosis. Tubercle bacilli may spread over a larger 

 area, for instance in the pleura, the peritoneum, the liver, or the 

 spleen, in'such a manner as to form numerous small tubercles, which 



