OVINE CASEOUS LYMPH-ADENITIS 213 
the nodule and prevent its further growth is obtained. The nodules 
in the kidneys and lungs present a similar microscopic appearance, 
excepting that the foci in the lungs are more regular-on account of the 
catarrhal inflammation that accompanies the reaction of the sur- 
rounding tissue. The center contains a dense mass of disintegrated 
cell structures, composed of the desquamated and proliferated epithe- 
lial cells, degenerated leucocytes and round cells. In experimental 
animals which succumb quickly to an intravenous injection of virulent 
material, the lung tissue immediately surrounding the nodules is 
frequently 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 degenera- 
tion and death of the latter. Simultaneously a slow chronic inflam- 
mation 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 exception 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 after- 
wards. In the centre of the older purulent or caseous mass (for the 
consistence varies from that of cream to that of cheese in different 
tumors) there are usually present no bacilli which can be demon- 
strated by the microscope or by cultural methods. 
Diagnosis. The diagnosis is made by the symptoms, lesions and 
the finding of the specific bacterium. There are no specific reactions 
for diagnostic purposes. This disease is to be differentiated from 
infections of various kinds, not recognized as specific, which may 
cause enlargement or suppuration of lymph glands. The specific 
infectious diseases, such as tuberculosis. Lymphadenoma and in 
case the lesions are restricted to the lungs or organs other than lymph 
glands, from parasitic lesions. In cases of parasitic lung or liver 
nodules the intestinal wall is usually affected. 
If the diagnosis cannot be made from the gross appearance of the 
lesions a bacteriological examination will be necessary. The fact 
should be kept in mind that tuberculosis in sheep is very rare. In 
