Anatomical Changes. 



539 



It is usually possible to demonstrate tubercles with giant cells in fresh 

 villosities. Some of these, however, do not show a tuberculous structure nor does 

 their inoculation into guinea pigs produce tuberculosis. (Heymans found tubercle 

 bacilli, virulent upon inoculation, in only 58 out of 70 excresences examined.) 



The lymphatic glands in the region of the diseased organs 

 are always involved. On the other hand they are not infre- 

 quently, especially in young animals, the sole seat of the disease. 

 At first they are only homogeneously swollen and enlarged and 



Fig. 82, Tuberculosis of Thoracic Onjuns of Cattle, a and h enlarged tuberculous 

 bronchial and mediastinal glands ; c and d pearly tumors on the pericardium and 

 pleura; e trachea; f esophagus. Cheesy nodules in the lung substance. 



more or less hemorrhagic ; later on a section will show spotted 

 turbidities in a grayish-red background. The turbidities con- 

 tain tubercles or diffuse caseous masses. At a later stage the 

 glands develop into large firm tumors consisting of grayish- 

 white fibrous tissue in which are imbedded large foci of a dry 



