BACILLUS PSEUDOTUBERCULOSIS GROUP 



239 



the disease and its organism, which showed it to be of considerable 

 economic importance in sheep and to be quite generally distributed. 

 This organism is not to be confused with the pseudotuberculosis 

 bacillus of Pfeiffer infecting guinea-pigs. The latter is wholly 

 different, and belongs to another group entirely. 



Distribution. The disease in sheep has been reported from 

 Europe, South America, and North America, particularly in aged 

 sheep. 



Morphology. Bacillus pseudotuberculosis is a short, straight 

 rod, with rounded ends, quite variable in size, about 0.4 ^ by 

 1.3 to 1.6 u or longer. Sometimes clubbed types are observed, the 

 enlarged portion staining more intensely than the remainder, 



Fig. 102. Bacillus pseudotubercvlosis, colony and mount (Norgaard and 

 Mohler in Report of Bureau of Animal Industry). 



reminding one of somewhat similar types in the B. diphtheria. 

 Chain formation rarely occurs; the organisms are usually found 

 in pairs. It is non-motile, and produces no spores or capsules. 

 It stains readily with the ordinary anilin dyes, and is gram- 

 positive. 



Isolation and Culture. Cultures may be obtained in pure 

 condition by opening a caseous nodule and making smears upon 

 agar. Growth is scant at first, but becomes better after a time, as 

 the organism adapts itself to growth on artificial media. The 

 discrete colonies produced by the initial inoculation grow in twelve 

 days to a diameter of 4 to 6 mm.; they are rounded, thick, gray- 

 white in color, with a waxy and granular surface, and with con- 



