Abstract
A stock of 500 guinea-pigs at the Lister Institute was attacked by an epizootic and only 21 survived. These survivors showed definite immunity to a bacillus of the food-poisoning group (indistinguishable from B. aertryck and the B. suipestifer) recovered frequently from animals dying during the epizootic. Five of them have been proved to be carriers excreting the bacillus intermittently five month's later and the serum of all of them agglutinates the bacillus. Spread of infection apparently did not occur amongst contacts placed with these carriers in the few experiments carried out.