575 
1908-9.] The Pathogenesis of Micrococcus melitensis. 
that in rodentia at any rate an active immunity to M. melitensis is never 
acquired. Full-grown rabbits and guinea-pigs occasionally appear resistant 
to small doses of the micrococcus or doses of cocci of low virulence ; but this 
immunity is apparent rather than real, and a larger dose, or a similar-sized 
dose of a more virulent strain, or inoculation by some other channel, will 
always produce a successful infection. Hence the observed absence of 
bactericidal substances from the serum of healthy or infected rodents is not 
