A tendon receptor organ in Limulus

Abstract

1.1. The tendon receptor organ found in the trochanter of the legs of Limulus polyphemus Latreille consits of a small tendon-like structure which extends from the anterior to the posterior face of the trochanter close to its medial and proximal edge. A narrow accessory muscle originates on the nearby coxal surface and part of it inserts on the anterior end of the tendon. Another part of the accessory muscle curves around the tendon and inserts on one of the small tendons of the large femur flexor muscle. The latter orignates in the trochanter near the tendon organ.2.2. The tendon organ nerve supplies about thirty large neurons embedded in the anterior end of the organ. Also embedded in the tendon in the same area are about twenty peculiar cuticular bodies of varying sizes up to 200 μ. Some of the neurons are multipolar. Some of the dendrites end among and close to the cuticular bodies and others extend posteriorly along the long axis of the tendon and end some distance away.3.3. Normal stimulation of the proprioceptors is probably effected by relative movements of either the coxa-trochanter or the trochanter-femur joint as well as by contractions of the accesory muscle. Ultimately all stimuli are probably mediated via the accessory muscle. Preliminary electrophysiological results indicate that most of the sensory units are “position” types but with a very wide distrubution of adaptation times.4.4. The tendon organ proprioceptors probably monitor the movements of two joints in cotrast with the membrane receptors of a given joint which monitor one.