An Organ for Proprioception and Vibration Sense in Carcinus Maenas

Abstract

1. An organ lying across the propodite-dactylus joint of the walking leg of Carcinus maenas has been described; this organ is supplied by a nerve bundle which contains some large fibres (up to 20µ in diameter) and which accompanies the motor nerves to the flexor of the dactylus. A similar organ lies in the meropoditecarpopodite joint. 2. The organ is embedded in a strand of elastic tissue which is in a stretched condition at all positions of the joint, the stretch being greater the more the joint is flexed. 3. The organ with its afferent nerve has been isolated and shown to contain sensory receptors. It reacts to vibration and to sudden changes in length with a burst of impulses in both large and small fibres. There is a resting discharge in small fibres which varies with length. 4. Experiments on the organ in situ show that it can serve to signal the rate and extent of movement in the propodite-dactylus joint. In addition, it may be used as a vibration-receptor. It is probable that some of its nerve fibres can signal the position of the joint and the direction of movement.