VARIATION OF SALMONELLA PULLORUM 39 



evidently possessed some power of stimulating a local tissue reaction, which was 

 entirely absent in chicks inoculated with other variants. 



These results definitely show that Variant IX-b can invade the natural host 

 beyond the point of inoculation, as well as cause local tissue response without 

 undergoing an alteration in colonial and cellular morphology. Furthermore, little 

 or no increase in virulence was observed. However, this conclusion may not be 

 justified since the experiment was not designed for such a determination. 



No. 4. Ten chicks were inoculated subcutaneously with 0.4 cc. of a suspen- 

 sion of Variant XH-b. No mortality resulted from the injection. The variant 

 strain was recovered from three of the killed chicks. In two instances the organism 

 was isolated from the yolk, and in the third, from the spleen, which indicates that 

 the organism had definitely invaded the host and established itself. A marked 

 thickening of the yolk capsule, due to infection, was observed. The isolated 

 organism resembled the original variant in colonial and cellular morphology. 

 (See Figures 18, 64 and 65.) In only one instance was local tissue response evident 

 at the time of necropsy. Variant Xll-b is characterized by the filamentous por- 

 tion of its colony, and this feature apparently is little affected through animal 

 passage. 



No. 5. Twelve pullets which were approximately four months of age were 

 inoculated subcutaneously with suspensions of eight variants (A, B, C, D-l, E, 

 Vl-a, VHI-a, and IX-a) and four so-called normal strains (IV, XIV, 11,706, and 

 18,292). Three injections of 2 cc. each were administered on alternate days. 

 Approximately three weeks after the last injection, all birds were necropsied. 

 No clinical manifestations were observed as the result of the inoculation. Table 

 12 shows the response of the different strains in the living host. Five birds inocu- 

 lated with variants failed to produce agglutinins. Also, the organism was not 

 recovered at necropsy. Two birds inoculated with typical strains did not yield 

 S. pullorum at necropsy, but their sera agglutinated pullorum antigen. Three 

 variants (C, D-l, and E) and two so-called normal strains (XIV and 18,292) 

 were recovered from the birds. The different variants did not lose their character- 

 istic features to any extent, as the result of passage through the host. (See Figures 

 66-68, inclusive.) Strain XIV exhibited typical colonial features, but the cells 

 appeared pleomorphic in smears prepared from meat extract and liver infusion 

 agar. Antigens prepared from the isolated organisms all exhibited atypical reac- 

 tions, with the exception of that prepared from Strain 18,292. 



S. pullorum was observed in stained tissue impression smears from chicks and 

 adults that yielded pure cultures of the organism on necropsy. The morphology 

 of the organism in a few instances appeared atypical and slightly larger than the 

 normal type, but as a rule a very close resemblance was seen. (See Figures 69-74, 

 inclusive.) Extreme pleomorphic forms were never detected, and it is doubtful 

 whether such forms ever occur in the natural host. However, organisms which 

 possess the potentialities of reproducing pleomorphic types on artificial medium 

 do exist, as has been reported. 



In a brief summary concerning the data presented in the different experiments 

 of this part, it may be stated that variants of 5. pullorum may settle out in broth 

 cultures, but that the degree of settling will vary among the different variants. 

 Likewise, the stability in NaCl solution will vary among different types, and 

 even fluctuate within the same type. The ability to attack different fermentable 

 substances appears to be changed but little, if any, for all variants. Sojourn in 

 fresh whole eggs and in the natural host apparently had little or no influence on 

 the general features of the different variants. 



