THE possibility that the spinal cord might form part of a continuous neural pathway along which tetanus toxin can pass from a peripheral site of infection in a limb to bring about a fatal intoxication of the brain stem, was first examined experimentally by Meyer and Ransom (1903). They compared the survival times of two cats, both of which had received a lethal dose of toxin by intraneural injection into the sciatic nerve, but one of which had had its spinal cord transected a t the upper lumbar level shortly before. The cat with the transected cord developed spastic tetanus in both hind limbs, but at no time showed any sign of intoxication above the level of the transection, whereas the control animal died with generalised tetanus on the fXth day. This type of experiment was soon afterwards repeated by Tiberti (1905) on two dogs with transected cords, but his results were equivocal in that both died after six days at the same time as a similarly inoculated control dog with an undivided cord.Since these early observations, the question of the ascent of tetanus toxin in the spinal cord has been re-examined by two groups of investigators who have reached diametrically opposed conclusions.Firor et al. (1940) studied the problem in groups of dogs with intact and transected cords, in both of which small doses of toxin were later injected into the lumbar enlargement below the level of the division. From these experiments, they reached the conclusion that in the intact animal the lethal agent does not pass upwards to the vital centres either in the cerebrospinal %uid or within the substance of the cord itself. They were led to suggest that this agent was carried from the lumbar cord to the brain stem in the circulating blood. Friedemann et al. (1941), on the other hand, interpreted the results of a comparable series of experiments differently. They found that in monkeys whose cords had been transected, the tetanus that followed an intramuscular inoculation of toxin into one hind limb remained confhed t o the lower extremities, whereas in monkeys with intact cords, a similar inoculation led rapidly to a generalised and fatal form. From this difference in outcome, they inferred that the division of the cord above the emergence of the lumbar plexus prevented the intoxication of vital centres higher in the central nervous system.
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