MORBID ANATOMY 241 



animal, which has been destroyed three weeks after inoculation, 

 is examined microsopically the following picture is obsefved : 

 A caseous center composed of an amorphous material that does 

 not take any of the ordinary stains. Surrounding the center 

 may be seen numerous leucocytes more or less degenerated and 

 frequently containing one or more bacteria, while clumps of 

 these organisms are scattered among them. External to this 

 is a dense round cell infiltration, the peripheral zone of which 

 is undergoing connective-tissue formation, thus serving as a 

 line of demarcation between the atrophied liver cells and the 

 central cell mass. The process then repeats itself until a con- 

 nective-tissue barrier strong enough to encapsulate the central 

 part of the nodule and prevent its further growth is obtained. 

 The nodules in the kidneys and lungs present a similar micros- 

 copic appearance, excepting that the foci in the lungs are more 

 regular on account of the catarrhal inflammation that accom- 

 panies the reaction of the surrounding tissue. The center con- 

 tains a dense mass of disintegrated cell structures composed ol 

 the desquamated and proliferated epithelial cells, degenerated 

 leucocytes and round cells. In experimental animals which 

 succumb quickly to an intravenous injection of virulent ma- 

 terial, the lung tissue immediately surrounding the nodules is- 

 frequently seen to be hepatized. 



According to Gilruth the lesion commences by the arrest 

 of the specific bacterium generally in a lymph-gland where one 

 or more are surrounded by and included within the phagocytes. 

 The micro-organisms multiply within the cell and ultimately 

 cause the degeneration and death of the latter. Simultane- 

 ously a slow chronic inflammation occurs around the focus of 

 attack ; there is proliferation of connective tissue-cells and the 

 formation of more or less new fibrous tissue. As the process 

 spreads outwardly the centre degenerates, and the protecting 

 wall increases in thickness. In fact, all the phenomena of the 

 pathology of true tuberculosis in a gland occurs, with the ex- 

 ception of the formation of giant cells. The degenerated centre 

 of the nodule assumes a greenish tint, especially distinct at the 

 time of exposure by the knife, but becoming gradually grayer 



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