536 Tuberculosis. 



pathogenic organism in preparing a soil for the tubercle bacillus. 

 The pronounced intermittent fever observed in advanced cases 

 of tuberculosis is usually an indication of an infection with 

 pyogenic bacteria causing suppuration in tuberculous organs. 



According to Oestern the bacterial flora in soft tuberculous foci is a very 

 limited one. Besides tubercle bacilli there are chiefly staphylococci, especially 

 staphylococcus albus; sarcina and bacteria resembling colon bacilli are rarely found; 

 streptococci are absent. If only tubercle bacilli are present the mass is yellow 

 and of a slimy watery consistency. Otherwise these soft foci are caseo-purulent or 

 muco-caseous. Bongert has shown however that in cattle the purulent softening 

 of the tuberculous tissue is caused almost exclusively by tubercle bacilli, especially 

 when these bacilli are destroyed in considerable numbers. 



Anatomical Changes. The tubercle which is the charac- 

 teristic product of tuberculosis, is at first a gray and transparent 

 nodule, just visible to the unaided eye, but soon becomes yel- 

 lowish as a result of cheesy degeneration which commences 

 in the center. Nodules of the size of millet seeds or larger 

 are the result of fusion of a number of primary nodules. The 

 continuation of this process of fusion or conglomeration leads 

 to the formation of still larger, dry, yellow cheesy masses or 

 foci. The tuberculous nature of these is indicated by the pres- 

 ence of characteristic tubercles in the tissue immediately sur-- 

 rounding them. Tubercle formation and caseation are, in 

 general, the characteristic pathologic-anatomical changes in 

 tuberculosis (but considerable variations may be present in 

 different species as well as in different organs). 



In cattle the thoracic organs, especially the lungs and the 

 broncho-mediastinal lymph glands are the chief seat of disease. 

 In the tissue of the lungs there are foci of all sizes, which may 

 be firm and sharply circumscribed; the surface on section ap- 

 pears reddish-gray or yellow, their substance consists of a dry, 

 crumbling, cheesy or mortar-like mass surrounded by tough 

 connective tissue; on the other hand they may consist of soft 

 yellowish-white masses of pus surrounded by a thin connective 

 tissue capsule. The presence of such foci is immediately 

 recognized by the nodular appearance of the surface of the 

 lung or by palpation of the deeper seated nodules. Their size 

 varies considerably. In advanced cases there are all transition 

 stages from the small gray nodules just visible to the unaided 

 eye up to tumors larger than a man's fist. In the tissue sur- 

 rounding the large tumors there are almost always new-formed 

 tubercles resulting from the migration of bacilli through the 

 lymph spaces. Foci of embolic origin are usually found in the 

 interstitial tissue of an otherwise healthy portion of the lung. 

 The pulmonary tissue between the various tuberculous tumors 

 may be either normal, or through the filling up of the alveoli 

 with exudate it may be of a homogeneous reddish-gray or yel- 

 lowish appearance. As a result of proliferation of the inter- 

 stitial connective tissue certain areas become thickened and 

 tough and partly or wholly devoid of air. According to the 

 severity of the disease only a portion of the organ may be 

 affected (in cattle usually the posterior lobes in swine the an- 



