Fact and fallacy in measurement of conduction velocity in motor nerves

It is necessary to examine the possible fallacies before one can accept any statement as 'fact'. This paper will attempt to assess the importance of the more obvious fallacies inherent in the method of measurement of conduction velocity as determined by length and latency measurements and will not take account of possible biological variables such as age of the subject. Only the method of computation by length and latency differences between two stimulated points on a nerve will be considered, as the latency of muscle response from a single peripheral stimulus includes unknown variables, including slowing due to terminal branching, conduction by non-myelinated terminals (at a rate of the order of 03 m./sec. according to Katz and Miledi, 1963), junctional transmission, and propagation from motor end plates to the recording electrodes. Comparisons of latency may usefully be discussed, but not velocity (Simpson, 1956). These difficulties are eliminated if the evaluation is limited to a stretch of nervewhichcanbe stimulated at two points, since the region of uncertainty is excluded from the calculations, but certain methodological difficulties remain.