Subparalytic doses of s were given to three observers. Four major perceptions were reported: (1) displacement or repostttonmg,of the perceived visual world in the direction of a successfully executed eve movement: (2) jumping durmg a saccade; (3) mocmrent associated with drift of the eye; (4) increased effort associated with each eye movement. Paralytic doses of succinvlcholine were administered to a single observer. Three major perceptions were reported: (1) displacement in the direction of the intended eye movement without jumping: (2) a sensation that great effort was required to move the eye; (3)fading of the visual image due to effective retinal stabilization. Similar visual perceptions were observed when the eye was paralyzed with a local anesthetic: however, no fading or sense of effort was reuorted. No deficits in oattern vision (except for intermittent fading) were reported in any of the studies. When the normal eye is voluntarily moved to a new position, the optical image makes a transition on the retinal surface, yet our perception is of a stable visual and spatial world. Helmholtz (1867) first pointed out that if one pushes the globe with a finger the optical image also makes a transition on the retinal surface; however, unlike the normal perception described above, we perceive a displacement of visual space. This simple experiment led Helmholtz to conclude “our judgments as to the direction of the visual axis are simply the result of the effect of will involved in trying to alter the adjustment of the eyes”. That is, our perceptions of space must in part be calculated centrally from a motor outflow to the extraocular muscles rather than from a sensory feedback. Mach (1886), Hering (1879), Jackson and Paton (1909) all later produced evidence which further suggested that our sense of visual space is independent of extraocular sensory feedback. Sperry (1950) and Holst (1954) have called this central monitoring of extraocular motor outflow a “corollary discharge” and “efference copy”, respectively. We will not discuss details here, since this literature has been extensively reviewed (MacKay, 1974, 1973; Dichgans and Bizzi, 1972; Evarts, 1971; and Merton, 1964). If a corollary discharge is in fact used centrally to calculate visual space, one would expect that extraocular paralysis would produce an illusory spatial displacement during voluntary eye movements. Several sources support this prediction. Clinically, for example, it is well known (Cogan, 1956; Jackson and Paton, 1909; Helmholtz, 1867) that pathological weakening or total paralysis of the extraocular muscles produces past pointing (spatial mislocalization). This past pointing is always in the direction of the attempted eye movement. Experimentally, ‘Send reprint requests to: John K. Stevens. Dept of Physiology IG4. School of Medicine. University of Pennsylvania. Philadelphia. PA 19174, U.S.A. Kornmueller (1931) reported that weakening or paralysis of the extraocular muscles using a local anesthetic produced past pointing and illusions of spatial displacement. He stated that when “glance intentions” were attempted, a striking apparent displacement in the direction of the intended eye movement was perceived. Brindley and Merton (1960). Siebeck (1953, 1954) and West (1932) also described a similar apparent displacement in subjects given low doses of curare. Quite surprisingly, however, Siebeck (1953, 1954; Siebeck and Frey, 1953) found that when subjects were totally paralyzed with high doses of a neuromuscular blocking agent no illusion of spatial displacement was eDer reported. The subjects reported only that they had the subjective sensation that their eyes were paralyzed. It should be emphasized that these results are in direct contradiction to the motor outflow theory. The present series of experiments were designed to help resolve this contradiction. It is clear that to study the perceptions associated with extraocular paralysis it would be necessary to use all three forms of experimental paralysis discussed above. Accordingly, we produced: (1) partial paralysis with systemic low dose injections of curare to mimic the experiments of Brindley and Merton, West and Siebeck; (2) total paralysis using systemic injections of a neuromuscular blocking agent to replicate Siebeck’s total paralysis study; and finally (3) retrobulbar blocks with local anesthetic similar to Kornmueller’s procedure. Partial pnralysis METHODS Three of us served as observers in the low dose studies (RCE. ACR, JKS) and curare (624mg) was used as the paralyzing agent. Observations were always made during the induction period of the total paralysis studies and six experiments were carried out specifically for study of low dose effects. The same procedure and precautions described below in the total paralysis section were observed. Audio tapes were made of experiments, and transcripts were later typed.