EN
There was noted a high grade of sensibility of the louse Polyplax spinulosa Burm on the infoction with the virulent bacilli Brucella brucei. There was also proved a great sensibility of the louse Hoplopieura acanthopus on the infection with Brucella, this time with non-virulent strain S₁₉. We failed to infect experimentally the mite Gamasides with the bacilli Brucella which confirmed the results of our former experiments. In the investigations of the structure of colony, the activity of enzymes, the production of H₂S and the sensibility on thionine and fuchsine, the strains isolated from the louse Polyplax spinulosa Burm. were not different from the same strains before their entrance into the organism of the louse. Hamsters Mesocricetus auratus proved very little sensible on the infection with the virulent bacilli Brucella brucei. The results of the quoted experiments indicate the role of the louse in the circulation of bacilli Brucella among animals.