GENUS BACTERIUM 



261 



the organisms varies with the media upon which it multiplies. 

 On blood serum and egg media the organisms are nearly 

 constant in form and size and slightly smaller than they 

 usually appear in the tissues 

 of the infected fowl. On 

 glycerin agar they vary, ex- 

 cluding occasional long invo- 

 lution forms, from two to six 

 /* in length, a large majority 

 of the individuals ranging be- 

 tween two and five /*. The 

 average length of a large 

 number was 3.9 ^ the width 

 varied from 0.3 to 0.7 /*. In 

 Id cultures the variation in 

 the size of the individuals is 

 more marked. In cultures 

 from three to six weeks old a 

 large number of the individu- 

 als contain granules which 

 stain deeply. When but two 

 are present they are near the 

 poles. Occasionally the long- 

 er rods contain three or more 

 granules. If there is but one 

 granule it usually appears 

 near the middle of the organ- 

 ism. These granules are very 

 similar in appearance to 

 those described by Wolbach Fig. 59. Avian tubercle bacteria, 

 and Ernst 31 in the human * bacteria in a cover-glass prepa- 



and bovine varieties. In old r f ion / rom ? ^berculous liver 



14, . f a fowl; 2, photograph of a 



(lures involution forms preparation from a glycerin agar 



are numerous. culture. 



Pure cultures were obtained by inoculating glycerin 

 and blood serum tubes directly from tuberculous livers 

 Ernst, loc. cit. 



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