Quantitative Aspects of Tonic Immobility in Vertebrates

Abstract

An experimental analysis of tonic immobility, or "animal hypnosis," in the lizard Anolis carolinensis leads to the assumption of the existence of 2 independent inhibitory hormones. These hormones are assumed to maintain tonic immobility, when present above threshold concentration, by inhibiting impulses from "higher nervous centers" and by allowing impulses to pass from the tonic centers to the muscles.