CULTIVATION OF BACILLUS 



489 



large globular, oval, or pyriform 



Fig. 146. — Bacillus of plague from a young 



culture on agar. 

 Stained with weak carbol-fuchsin. x 1000. 



striking variety of shapes, 

 bodies resulting (Fig. 

 148); with about 2 per 

 cent, sodium chloride, after 

 twenty-four hours' incuba- 

 tion, the most striking 

 feature is a general en- 

 largement of all the bacilli. 

 Sometimes in the tissues 

 they are seen to be sur- 

 rounded by an unstained 

 capsule, though this ap- 

 pearance is by no means 

 common. They do not 

 form spores, and are non- 

 motile. They stain readily 

 with the basic aniline stains, 

 but are Gram-negative. 



Cultivation. — From 

 the affected glands, etc., 



the bacillus can readily be cultivated on the ordinary media. 

 It grows best at the temperature of the body, though growth 



occurs as low as 18° C. 

 On agar and on blood 

 serum the colonies are 

 whitish circular discs of 

 somewhat transparent 

 appearance, and smooth, 

 shining surface. When 

 examined with a lens, 

 their borders appear 

 slightly wavy. In stroke 

 cultures on agar there 

 forms a continuous line 

 of growth with the same 

 appearance, showing 

 partly separated colonies 

 at its margins. When 

 Fig. 147.— Bacillus of plague in chains show- a g ar cultures are kept at 



in g boumon. taini " g ' Fr ° m * y ° Ung CUUUre the room temperature, 

 Stained with thionin-blue. x 1000. some of the colonies may 



show a more luxuriant 

 growth with more opaque appearance than the rest of the 

 growth, the appearance in fact being often such as to suggest 



