SUMMARY: The development of tetanus intoxication in the frog is dependent on the environmental temperature being above about 15". The incubation period and time to death become shorter as the environmental temperature is raised. Cooling below about 15° prevents both the fixation of the toxin and its action after fixation but does not increase the speed at which the toxin is destroyed or excreted. The absorption of the toxin after injection into the dorsal lymph sac is not prevented by cooling. It is possible to produce local tetanus in frogs by the intramuscular injection of tetanus toxin, but the dose needed for this is very critical. In most cases either generalized tetanus develops or there are no signs of intoxication. However, local tetanus can regularly be produced when the toxin is given intramuscularly to frogs partially protected from generalized tetanus by an injection of tetanus antitoxin given via the dorsal lymph sac. The local tetanus so produced does not progress to involve the opposite limb. The muscular spasm is abolished by cutting the motor nerve or by general anaesthesia. Tetanus toxin appears to act on the central nervous system of the frog in the same manner as in mammals. However, frog brain tissue does not neutralize tetanus toxin in low concentrations as does mammalian brain tissue, but concentrated tetanus toxoid gives immediate protection to frogs in the same way as it does in mammals.