212 OVINE CASEOUS LYMPH-ADENITIS 
characteristic, closely resembles the contents of the intestinal nodules 
produced by Oesophagostoma columbianum. In very advanced cases 
the internal organs may contain lesions which macroscopically 
resemble those of tuberculosis. The lungs may be studded with 
small nodules the size of a pea, the spleen, liver and in rare instances 
the kidneys also may contain one or more foci of the same character, 
namely, a mass of greenish-yellow material, surrounded by a firm, 
fibrous wall. The bronchial and the mediastinal glands may be 
affected without lesions being found in the lungs. In some cases the 
lungs contain nodules varying in size from that of a millet seed to that 
of a walnut. This condition is, as a rule, accompanied by a chronic 
pleurisy with extensive adhesions and also effusions into the pleural 
cavities. 
The liver may contain nodules similar to those in the lymphatic 
glands. Cases have been reported, however, where the entire organ 
was thickly sprinkled with miliary nodules. 
The kidneys are rarely affected, but when they are the lesions 
assume the same characteristic appearance of a firm walled abscess 
protruding on the surface of the organ. As a rule, only one to two 
such foci are observed in each case. 
A histological examination of tissues containing miliary nodules 
shows them to be composed chiefly of leucocytes and round cells. 
Toward the center they are degenerated into a granular detritus. 
Giant cells are not observed. Among the cells are seen the short 
bacteria arranged singly or in clumps. They stain irregularly. The 
bacteria are frequently seen within the degenerated leucocytes, the 
destruction of which is due, according to Preisz, to the specific chemi- 
cal products elaborated by the microérganisms. 
When a miliary nodule from the liver of an experimental animal, 
which has been destroyed three weeks after inoculation, is examined 
microscopically the following picture is observed: 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 peri- 
pheral 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 connec- 
tive-tissue barrier strong enough to encapsulate the central part of 
