The Localized Action on the Spinal Cord of Intramuscularly Injected Tetanus Toxin

Local tetanus limited to one leg was studied in cats after intramuscular injection of tetanus toxin. 1. The electric and mechanical response of the affected muscle after a single stimulus to the intact sensory-motor nerve is greater in amplitude and duration than the response of the corresponding muscle of the unaffected leg (Fig. 1). 2. This augmented response of the muscle is associated with an augmented response arising from the ipsilateral portion of the spinal cord, while the contralateral part of the cord is unaffected, as demonstrated by electrographic records from the motor nerves (Figs. 2 to 5). 3. The augmented muscular response is abolished when the reflex arc is broken, but the augmented response in the spinal cord is independent of changes in the muscle, the neuromuscular junction, the afferent and efferent peripheral nerves, and the dorsal root ganglia. 4. The augmented spinal response develops in the absence of the peripheral signs of local tetanus. Hence the pathogenesis of the altered state in the spinal cord is independent of the peripheral effects of the toxin. 5. In local tetanus, therefore, the toxin injected intramuscularly acts selectively upon the segments of the spinal cord which supply the innervation of the injected area. 6. The augmented spinal response may be prevented by section of the nerve trunks supplying the area of injection prior to the injection of the toxin. 7. It is concluded that in local tetanus the toxin is carried to the spinal cord by way of peripheral nerves.