Peter Matthews showed quantitatively that the primary endings of muscle spindles measure length and rate of lengthening muscle, and the secondary endings measure length only (the full experimental development of Sybil Cooper’s discovery). He also showed that there are two classes of fusimotor fibres: dynamic, which adjust the velocity sensitivity of primary endings, and static, which adjust the length sensitivity of primaries and secondaries.

Peter revealed that the tonic stretch reflex is abolished by selectively paralysing the fusimotor fibres with procaine, a method now taken up by other laboratories; and that the primary endings, which can be selectively and maximally excited by vibration, unexpectedly cannot generate enough central excitation to account for the tonic stretch reflex, making it probable that the secondaries, whose reflex function has hitherto been obscure, are partly responsible. In addition, he showed that the primaries respond strongly to small maintained changes of length, a property important for the possible servo-initiation and servo-government of movement by the CNS. Peter’s monograph on muscle spindle physiology (1964) continues to have wide influence.

Professor Peter Matthews FRS died on 3 March 2020.