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D. W. BRUNER AND P. R. EDWARDS 



agar which contained serum derived from phase 1 of the Bispeb- 

 jerg type, culture HR yielded phase 2, 228 yielded a mixture of 

 phases 2 and 4, while the remainder of the organisms yielded phase 

 3 or a mixture of phases 3 and 4. For this reason mixtures of 

 serums were used to force variation in the desired direction. 

 The variations induced in one culture, strain 228, are given in 



Phase 



1 



B+4 > Phase 2 



*+•* > Phase 1 



B±* >. Phase 3 



_I » Phase l — ^ * Phase 2 



^ Phase 3 



Kt3 > P* 1 *" 1 



B+i. 



Fig. 1. Changes Induced in S. paratyphi A 228 

 Symbols on arrows indicate what serums were added to medium. 

 B, serum derived from phase 1 of Bispebjerg type. 

 K, serum derived from S. cholerae suis var. kunzendorf. 



3, serum derived from S. paratyphi A, phase 3. The serum was absorbed with 

 ohase 1 before use. „ . , , ... 



4, serum derived from S. paratyphi A, phase 4. The serum was absorbed with 

 phase 3 before use. 



figure 1. The changes produced in other cultures differed slightly 

 but they were all quite similar. 



When once isolated the induced phases of S. paratyphi A are 

 quite stable. No changes in the phases were noted during the 

 two years they were maintained in the laboratory. In this respect 

 they resemble the induced phases of E. typhosa and S. abortus-equi 

 and differ from the normal phases of the diphasic Salmonella 



109 



