ever, does not permit differentiation of the pyogenic class from 

 other long streptococci. 



COLLODIUM SAC EXPERIAIEXT.S TO IXCREASE VI III "LKXCK. 



It will be noted that none of these varieties were virulent at 

 the time of this study, further that the seven of my own isola- 

 tion was obtained from milk of healthy udders. Four strains 

 were sent to me by Mr. L. A. Holers of the Bureau of Animal 

 industry. (I have not. been informed as to the origin of the four 

 cultures sent by Mr. Rogers, except that Ihey are milk strep- 

 tococci.) 



Experiments have proved that streptococci originally viru- 

 lent may become nonvirulent after long cultivation on artificial 

 media, and that they may return to their original properties 

 after being passed through the bodies of susceptible animals. 

 For this purpose, collodium sacs were prepared. These were 

 filled with a beef-tea culture of the germ and placed in the 

 abdominal cavities of guinea pigs and rabbits. They were re- 

 moved after several days, the culture withdrawn and the viru- 

 lency of the same tested. The results are shown in the following 

 table : 



Table of attempts to increase virulence of milk streptococci. 



GUINEA-PIGS. 



