Tetanus toxin production in the absence of protein.

A modification of the Mueller medium for tetanus toxin production is presented, on which an adapted strain produces high yields of toxin (70 to 90 flocculating units per ml) in the absence of animal protein extracts. The range of iron concentration in the medium was established within which the toxigenic activity of the culture can be made to vary, and the mathematical nature of the variation is presented. Darkening of cultures during incubation indicates departure from optimal conditions. Heat input to the medium during autoclaving, originally undertaken solely for purposes of sterilization, is an important physicochemical factor in the toxigenicity of the culture.