BACILLUS PSEUDOTUBERCULOSIS RODENT1UM 367 



in the liver and spleen. Here numerous whitish round nodules are 

 formed, varying in size from a millet seed to a pea. They are sharply 

 defined from the surrounding tissue, project somewhat above the 

 surface, and contain a caseous centre. Such nodules are also occasion- 

 ally found in the kidneys. The abdominal lymphatic glands are 

 enlarged, and likewise contain nodules which have a tendency to 

 become confluent. Nodules are also found in the intestinal wall, 

 and particularly in the rabbit the appendix is a favorable seat for 

 them. They also involve the intestinal mucosa where they have 

 their seat in the lymph follicles. The lungs may likewise be affected, 

 and the process, according to Ligniere, may lead to purulent pleuritis 

 and peritonitis. The lungs, according to Nocard, are particularly 

 the seat of numerous nodules in pseudotuberculosis of chickens. 



Morphology. The Bacillus pseudotuberculosis rodentium of Pfeiffer 

 Is a short, plump rod of small size, generally 1 to 2 micra long, with 

 rounded ends. In older cultures and in the tissues ovoid forms are 

 seen. It has a marked tendency to form shorter or longer chains, 

 hence Dor called it a streptobacillus. It does not show any marked 

 motility in the hanging drop, but Klein claims to have been able to 

 demonstrate one or two flagella with the aid of van Ermengem's 

 silver impregnation method. The organism can be stained with the 

 ordinary watery anilin dyes; it often shows polar or peripheral staining, 

 particularly the ovoid forms. It is Gram negative. It is difficult to 

 demonstrate it in tissues, because it loses the stain so easily, but it 

 may be shown by Klein's method, which consists in first staining for 

 one minute with anilin water gentian violet and then washing for four 

 minutes in iodine iodide of potash solution. The bacillus does not 

 form spores. 



Cultural Properties. The organism grows well on all of the ordinary 

 laboratory media. On gelatin plates it forms superficial, yellowish- 

 brown, fairly thick, irregular colonies with serrated edges, 1 to 2 mm. 

 in diameter. There is a nipple-like elevation in the centre of the 

 colony, surrounded by a marmorated periphery. The deeper colonies 

 are more regularly round than the superficial ones. The gelatin is 

 not liquefied, but a cloudy halo due to the formation of fine crystals 

 appears around it after some time. In gelatin stick cultures the 

 growth is best at the surface, rather poor along the stick canal, 

 giving the culture a nail-like appearance. Bouillon is clouded after 

 eighteen to twenty-four hours, and a pellicle is formed on the surface. 

 Later a dust-like sediment is formed. The alkalinity of the medium 

 becomes increased. There is no indol formation. On agar and 

 coagulated blood serum a surface growth with a mother-of-pearl luster 

 is formed. It has been compared, on account of the iridescence, to 

 a thin film of petroleum on water. The addition of glycerin to 

 gelatin or agar favors the growth. On potatoes the growth of cultures 

 isolated directly from lesions caused by the bacillus leads to a yellowish- 

 brown, later a brown growth, which has a certain similarity to the 



