OVINE CASEOUS LYMPH-ADENITIS Q11 
only a single gland is affected. The relative frequency with which the 
various glands become the seat of the lesions may be given as follows: 
prescapular, precrural, superficial inguinal, bronchial, mediastinal, 
sublumbar, deep inguinal and scrotal. Rarely the suprasternal and 
mesenteric glands are affected. Sivori mentions the mesenteric 
glands among those frequently affected. He fails, however, to men- 
tion the mesenteric glands as the seat of lesions in the detailed descrip- 
tion of twelve typical cases of caseous broncho-pneumonia caused by 
the bacillus of Preisz. 
Fic. 48. LUNG OF SHEEP STUDDED WITH NODULES (Gilruth). 
When first invaded by the bacterium, the adenoid tissue becomes 
hyperplastic and the gland enlarges to several times its original size. 
On section the surface is found to be edematous but otherwise normal 
in appearance. This is followed by the formation of various centers 
of degeneration which show concentric layers and gradually become 
confluent. Finally, the total volume of the gland is transformed into 
a homogeneous, caseous mass. At the same time the distended 
capsule increases in thickness and forms a sac which confines the semi- 
fluid, grumous mass. In rare instances the sac ruptures and when 
close to the surface the contents will be discharged. Under ordinary 
circumstances, the caseous contents become cohesive and _ sticky 
and of the consistency of putty. In very old cases the mass becomes 
dry and mealy, with little or no tendency to calcification. The 
greenish-yellow color of the caseous mass, which is stated to be most 
