Effect of tetanus toxin on the monosynaptic reflex.

Tetanus toxin was injected at various doses (0.1-10,000 mouse MLD/kg) into the gastrocnemius muscle of the left hind leg of the cat. The relative excitability of the monosynaptic reflex (MSR) was increased in the very early period of the intoxication decreased in the later period, during which the MSR of the gastrocnemius was either partially or totally depressed at doses as low as 10 mouse MLD/kg.