PARATYPHOIDBACILLUS FROM URINE OF A CARRIER 



507 



very few typical colonies that in turn were propagated to ascer- 

 tain whether they kept their typical aspect or reverted to the 

 atypical one. This, however, was not the case. From a typical 

 colony only typical ones grew in the subcultures. On the other 

 hand, when the atypical colonies had been transferred for a few 

 times the fully developed colonies showed only the atypical as- 

 pect. At the end of three weeks we had to deal with a culture 

 that never showed any sign of being a mixture of the two kinds 

 of colonies, and since has always kept its character. 



Thus it is shown that the atypical strain kept its new character 

 unaltered when propagated rapidly from one artificial medium 

 to the next. We thought it necessary to see if it would also keep 

 this character when living under pathogenic conditions. For 

 this experiment we used white mice, that were very susceptible 

 to inoculations with these microbes. After intraperitoneal injec- 

 tions of small amounts of living bacilli the animals died in about 

 twenty-four hours. From each mouse some blood was taken 

 and injected into a new one without being cultivated on arti- 

 ficial media first. As a control of the bacilli at hand cultures 

 were simultaneously made on litmus agar. After being in- 

 jected into 8 mice the microbe still gave only atypical colonies in 

 cultures. 



As we thought it to be of some interest to find out if the viru- 

 lence of the atypical strain had altered with the new character 

 we inoculated several white mice with measured volumes of agar 

 slope cultures of the atypical and the typical strain of the bacillus 

 and watched the time when the mice died. 



The result of this experiment was as follows: 



It will be noted that the typical strain kills the mice in smaller 

 doses than the atypical strain. It must, however, be remem- 



