in plant, 36, 184 universal applicability of, 12 mechanical, 1 retinal. _See_ Light simultaneous mechanical and electrical record of, 13 Retina. _See_ Light Sanderson, Burdon-, on electrical response in sensitive plants, 14 Spring-tapper, mechanical stimulus by, 23 Staircase effect in metal, 122, 186 in muscle, 122, 186 in plant, 37, 186 Steiner on retinal response, 149 Stimuli, maximum effect due to superposition of, in metal, 136 in muscle, 36 in plant, 36 Stimulus, advantages of vibrational, 25 and response, relation between, in metal, 134, 135 in muscle, 52 in nerve, 52 in plant, 52, 53, 54 in real and artificial retinae, 162 effect of different kinds of, 2 mechanical, by spring-tapper, 24 conditions for maintaining uniformity of, 26 means of graduating intensity of, 22, 96 vibrational, 24, 25, 26 Temperature, death-points in plants, 61, 63 effect of, on response in metal, 111 in photo-sensitive cell, 158 in plants, 32, 60-69 in retina, 158 increased sensitiveness in plant due to variation of, 66, 67 Vibrational stimulus, 24, 25, 26 Vision, binocular alternation of, 175 effect of various conditions on the period of binocular alternation of, 177 Visual images, revival of, 177 impression, unconscious, 178 impulse, chemical theory of, 148 electrical theory of, 149 phantoms, 179 recurrence, 174 Vital force, 13 Vitalism, 182 Waller on enhancement of nerve-response after continuous stimulation, 127 on relation between stimulus and response in muscle, nerve, and retina, 52, 162 on retinal response, 150, 156, 165 on reversal of response in stale nerve and retina, 11, 124, 164 on transformation from abnormal to normal response in nerve after continuous stimulation, 124 PRINTED BY SPOTTISWOODE AND CO. LTD., NEW-STREET SQUARE LONDON