Immunoelectrophoresis revealed an antigen-antibody response between 4 day metabolic products and 8, 12 and 16 day sera and between 4 day trypanosomal extract and 16 day serum.
Metabolic products from trypanosomes incubated at room temperature do not appear to be antigenic.
The limitations of immunodiffusion are discussed in reference to the results. It is suggested that some of the antibodies to metabolic products may be of the precipitating type while others are not.
Since a faint reaction also occurred between 4 day trypanosomal extract and 16 day serum, it may be concluded that metabolic products contribute to only a portion of the antibody response of the rat and are by no means the exclusive agents. They possibly work in conjunction with other metabolics within or on the surface of the trypanosome
