STUDIES ON CULTURE STRAINS OF EUROPEAN AND MURINE TYPHUS

1. A strain of European typhus (Breinl) has been carried in cultures by means of successive transfers for a period of 1½ years, the rickettsiae in such cultures being quite as numerous as in similar cultures of murine strains of typhus. 2. The virulence of the cultures of European typhus has remained constant throughout the period of cultivation, although, on the whole, the scrotal lesions caused by the later culture generations were somewhat less marked than those produced by the first generations. 3. A strain of murine typhus has been similarly carried in cultures for 4 years with no apparent loss in pathogenicity. 4. The characteristic scrotal lesion in murine typhus in guinea pigs is apparently referable to actual predilection of this strain for the tunica tissue rather than to the number of rickettsiae injected.