VARIATION OF SALMONELLA PULLORUM 19 



aging in broth were found to bring about variation in the majority of strains 

 examined. Other methods employed proved to be less successful. 



Influence of Frequent Transfer and Aging in Beef Infusion Broth 



Experiment I. In this experiment four strains were employed. The source and 

 history of the different strains are as follows: — 



Strain I — Received from Miss Murphy, Department of 



Bacteriology, Yale University, — a sub-strain 



of a culture isolated from the ovary of a hen 



in 1930. 



Strain II — Received from Miss Murphy, — a sub-strain 



of a culture isolated from a chick in 1929. 

 Strain III — Received from the Department of Veterinary 

 Science, Massachusetts State College, — 

 isolated from a chick in November, 1932. 

 Strain IV — Received from the Department of Veterinary 

 Science, Massachusetts State College, — 

 isolated from the ovary of a hen in October, 

 1932. 

 Strains I and II were regarded as partial variants, as the result of treatment 

 applied by Miss Murphy to bring about variation. In her attempts she was not 

 successful in establishing and maintaining a rough type. On plain meat extract 

 agar these two strains formed smooth and rough colonies, the latter varying in 

 degree of roughness. In broth, Strain I produced a flaky type of sediment, with 

 the supernatant fluid partially turbid; while Strain II gave a uniform turbidity, 

 with moderate sedimentation. Strains III and IV resembled a typical S. pullorum 

 strain in all respects. 



The strains were cultivated in 10 cc. of beef infusion broth containing 1 per cent 

 peptone, pH 6.8 — 7.0. Transfers were made daily for a period of two weeks. 

 After 24 hours incubation at 37° C, the broth cultures were held at room tempera- 

 ture. The character of growth in all broth tubes appeared to be similar to that 

 described above for Strains I and II. Likewise, Strains III and IV exhibited no 

 deviation from the normal type in broth. 



Meat extract agar plates were streaked with broth cultures inoculated prior 

 to the sixth transfer. Strains I and II revealed smooth and rough colonies. Both 

 strains produced a larger cell than did typical strains of S. pullorum. Cultures 

 III and IV exhibited no change. 



Each set of broth cultures, after being incubated for 24 hours at 37° C, was 

 streaked on plain meat extract agar plates. The colony type of the different 

 strains was little altered by frequent passage through beef infusion broth. 



Sixteen days after the first set of broth tubes was inoculated all broth cultures 

 were streaked on meat infusion agar (pH 7.0). Strain I produced a rough type 

 of colony, with a dense center surrounded by a granular outer area which was 

 veined. Some colonies resembled the characteristic grape-leaf type of the typhoid 

 colony. A few smooth type colonies were also observed. Colonies approaching 

 the rough type were more abundant in the older cultures. Strain II produced a 

 dull, dense, granular, and entire colony which was slightly irregular in outline 

 and raised in the center. The diameter varied from two to three millimeters. 

 Strains III and IV exhibited colony forms which appeared to be identical with 

 the original type. 



Slight variations in colonial morphology on the different plates were observed 



