[The Magendie law on spinal ventral and dorsal roots is still of current value]

The law of Magendie--that the spinal ventral roots are motor and the dorsal roots sensory--was recently questioned. It turned out that ventral roots contain a substantial proportion of unmyelinated sensory axons. This and other observations promoted theories that ventral roots might constitute an additional pain pathway. However, it has now become clear that sensory ventral root axons do not enter the CNS via the ventral roots. Instead, they either leave the ventral root at the PNS/CNS interface and either continue to the pia mater, or loop and return to the periphery. The law of Magendie seems still to be valid.