VARIATION OF SALMONELLA PULLORUM 33 



tion occurred. These results seem to show that, on the whole, the variants have 

 undergone very little or no change in their fermentative powers. 



Behavior in Fresh Whole Egg 



In this experiment seven variants (C, D-2, E, IV-a, IV-b, Vl-a, and IX-b) 

 and their parent strains were cultivated in fresh whole eggs. The purpose of this 

 experiment was to determine whether a natural environment, such as is found in 

 the whole egg, would bring about a change in the colonial morphology of the 

 variants and their parent strains. The fresh eggs were obtained from flocks that 

 had revealed no signs of pullorum infection for at least two years. The cultures 

 were suspended in 0.9 per cent saline solution and injected into the yolk through 

 a small opening in the shell with a hypodermic syringe. The opening was sealed 

 with hot paraffin after the inoculation. Measures for insuring sterility were 

 observed in every step of this process. The eggs were incubated at 37° C. At 

 each transfer tubes containing sterile saline solution were inoculated with yolk 

 from inoculated eggs. The saline-yolk mixture was then injected into fresh eggs. 

 Agar plates were also streaked with the saline yolk mixture, in order to check for 

 purity and to study colony morphology. During the first part of this experiment 

 transfers were made approximately once a week, while later the interval between 

 transfers was extended to two weeks. 



Table 7. — Influence of frequent transfer in fresh eggs on the colony 



MORPHOLOGY OF S. pullorum. 



Table 7 gives the number of passages in whole fresh eggs, the number of days 

 between transfers, and the colony type for each strain. The terms "S" and "R" 

 were selected to describe the type of colony produced. However, in this instance 

 these terms are employed in a relative sense. The appearance of a rough colony 

 may vary considerably, yet fall into the category of roughness; likewise, a culture 

 may resemble the "S" type more closely than the "R" form, yet not be identical 



