BACILLUS PSEUDOTUBERCULOSIS OVIS 369 



wethers, and particularly in older ewes, the fully developed disease 

 with extensive lesions, due to a long chronic course, is observed. 



Pathologic Lesions. The internal organs of animals which have 

 been sick with this disease for a long time show either smaller or 

 larger nodules, inclosed in a fibrous capsule, containing a caseous 

 material, greenish yellow in color, and resembling the contents of the 

 intestinal nodules due to the intestinal parasite Esophagostoma 

 columbianum. The caseous nodules may reach the size of a walnut; 

 they are generally found in the lungs, spleen, and liver, and more 

 rarely in the kidneys. If the lungs are considerably involved the 

 pleurae are thickened and adherent; the thoracic cavity often contain 

 a pleuritic exudate. In the liver numerous small nodules looking 

 like miliary tubercles are sometimes found instead of the abscesses 

 with caseous material. According to Noergaard and Mohler, who 

 have studied the disease in this country, the principal changes in 

 cases not too advanced are generally confined to the lymph glands; 

 sometimes only a single gland is involved. The glands most com- 

 monly affected are, in the order of their frequency: the prescapular, 

 precrural, superficial inguinal, bronchial, mediastinal, sublumbar, 

 deep inguinal, and scrotal, and rarely the suprasternal and mesenteric 

 glands. Microscopic examination shows that the caseous mass is 

 composed of an amorphous material surrounded by more or less 

 degenerated and also intact polynuclear leukocytes. These are 

 again surrounded by fixed connective-tissue cells of the small mono- 

 nuclear and the endothelial type. Giant cells have never been found. 

 The inflammatory cells are surrounded by fibrous connective tissue 

 which forms the limiting capsule. The pseudotubercle and the true 

 tubercle, according to Grabert, may be distinguished by the following 

 differential characters. While both kinds of tubercles lead to caseation, 

 the pseudotubercle only very rarely shows calcification, but more 

 frequently desiccation with onion-like moulding of the dried layers. 

 If pseudotuberculous material is inoculated into the anterior chamber 

 of the eye, small nodules appear after two to three days, while true 

 tuberculosis leads to nodular formation only after two to three weeks. 

 The pseudotubercle is softer than the genuine one and not grayish 

 white and translucent like the latter, but white or yellowish and 

 perfectly opaque. In old pseudotuberculous nodules, with caseous 

 material young, small tubercles are not seen at the periphery as in 

 true tuberculosis. Pseudotuberculosis ovis is due to a bacillus 

 discovered in 1891 by Preisz and Guinard. 



Morphology. The Bacillus pseudotuberculosis ovis is a very small, 

 slender rod, only slightly thicker than the bacillus of hog erysipelas. 

 It has rounded ends, and the rods are from two to four times as wide, 

 sometimes even longer, and they vary considerably in shape. The 

 ends are sometimes club-shaped, in other rods they are pointed. 

 The bacilli in the discharge from the nodules are often seen in dense 

 groups, both inside and outside of the cells. In caseous material 

 24 



