Interspecies comparisons for the C3-C4 propriospinal system: unresolved issues.

There are conflicting views on the functional importance of the system of C3-C4 propriospinal neurones in the macaque, although the two sets of observations from the opposing laboratories are actually quite similar, both making the system appear much weaker than its well-known equivalent in the cat. One group asserts, mainly via evidence derived from experiments with strychnine, that this is a consequence simply of inhibition of the propriospinal neurone. However, we ague here that this judgement is premature and that much more needs to be known about the neurones involved and their connectivity before the analogy with the system in the cat is safe. This is particularly important because of a similar analogy which has been made with respect to measurements in human subjects.