272 



MICROBIOLOGY 



are oval, and the shorter forms resemble micrococci. The size 

 depends upon the medium and the stage of development of 

 the individual bacteria. A capsule has not been demonstrated, 

 although often in preparations made directly from tissues 

 there appears to be one. It is not observed in cultures. Spores 

 have not been seen. Involution forms are not uncommon in 

 old cultures. The bacteria are especially numerous in the 

 organs of a rabbit when it is allowed to lie for some hours after 

 death before it is examined. It exhibits, when stained in 

 cover-glass preparations made directly from animal tissues, a 



light center with deeply 

 stained extremities (polar 

 stain). In preparations 

 made directly from cul- 

 tures this character is much 

 less marked. 



Staining. It stains 

 readily with the basic ani- 

 line dyes. It does not stain 

 by Gram's method. 



Cultivation. This or- 

 ganism grows readily but 

 not luxuriantly on the or- 

 dinary alkaline media 

 made from meat infu- 

 sions. It does not grow in media having a decided acid 

 reaction. 



Agar. The growth on this medium is not vigorous. It 

 is of a neutral grayish color, with a glistening, moist appear- 

 ing surface. It is slightly viscid and adheres to the agar sur- 

 face. Isolated colonies vary from 1 to 2 mm. in diameter, 

 nearly round, convex, with smooth and sharply- denned mar- 

 gins. The condensation water becomes faintly clouded with a 

 grayish sediment which becomes viscid. Within the agar the 

 colonies appear as minute grayish dots. On agar, especially 

 in plates (Petri dishes), it emits a peculiar, disagreeable, 

 pungent odor. 



Fig. 60. Bacterium suisepticum 

 from a cover-glass preparation 

 of a rabbit's liver. 



