(1) In culture filtrates of Cl. chauvoei two antigens have been
demonstrated (a) a toxin, and (b) a heat stable antigen. The toxin
can best be demonstrated by injecting filtrate intradermically into
guinea-pigs, particularly if adrenalin is incorporated in the filtrate.
The presence of the heat stable antigen is proved if toxin-free
(heated) bacilli are injected into sheep; after a suitable interval
these are immune to the inoculation of living culture.
(2) The toxin, or its atoxic modification, stimulates the formation
of antitoxin when injected into animals, whereas the heat stable
antigen does not do so.
(3) The toxin is neutralizable by homologous antitoxin, by
Cl. septicum antitoxin and to a slight extent by the sera of some
normal bovines and rabbits.
(4) The toxins of four different strains of Cl. chauvoei have
been found to be indistinguishable serologically.
(5) There is no correlation between the amount of circulating
antitoxin in an animal and the power of the animal to resist the
inoculation of living culture.
(6) There is a correlation between the amount of circulating
antitoxin in an animal and its power of resisting toxin, injected
intravenously or intradermically.
(7) The evidence points to the heat stable antigen being the
important one in the production of immunity to Cl. chauvoei culture.