Abstract
An agar-diffusion method is described for the titration of Bacillus anthracis immunizing antigen and antibody. It is a sensitive and simple method that can be used for determining antigen concentrations in culture filtrates and for titrating antisera from animals and humans which have been immunized with the antigen. Marked improvements in yields of antigen in a defined medium and a hydrolyzed casein plus amino acids (Casamino) medium have been achieved with the aid of this assay method.