276 MICROBIOLOGY 



organism in the ova within the ovaries of hens, in the yolk of 

 the fresh egg, in eggs incubated for varying lengths of time, 

 and in yolk sacks of fully developed chicks still within the 

 shell. This suggests that the source of infection is the adult 

 and apparently healthy hen which was infected as a chick. 4 

 Whether or not this organism has a habitat outside of the 

 chicken body is not known. 



Morphology. A somewhat slender organism varying 

 from 2 to 3.5 ^ in length and from 0.3 to 0.5 /* in breadth. The 

 ends are rounded. It usually appears single, although pairs 



and short chains are some- 



, ' '. v times observed. It has a pro- 



nounced Brownian movement 



* which in some cultures might 



/ be mistaken for motility. 



'- , , , '. <_. Spores and capsules have not 



' . *. ' *' -,. ", ' / .j$g been observed. 



Staining. It stains read- 

 ily with the usual bacterial 

 stains. It does not take the 

 Gram stain. 



Fig. 61. Bacterium pullorum. Cultivation. There is no 



Photograph of a preparation difficulty in cultivating this 

 from an agar culture 36 hours organism on the ordinary 

 old. X 400. (Jones). ,. ,. ,. 



media directly irom the tis- 

 sues and blood of the recently dead chick. It requires for 

 rapid growth a temperature of 37 to 38 C. 



Agar. On agar small grayish white glistening convex 

 colonies appear in from 12 to 24 hours. In 48 hours they have 

 reached their maximum development having a diameter of 

 from 1 to 2 mm. When magnified they are found to be finely 

 granular. The growth does not become vigorous. The water 

 of condensation becomes slightly cloudy. 



Gelatin. Small whitish colonies appear in 48 hours. In 

 stab cultures a delicate grayish growth appears along the 



4 Dr. P. S. Jones in this laboratory is making a thorough investi- 

 gation of this point. 



