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rocks and of electric tourmalines. The invention of a new type of self-recovering electric receiver made of galena was the fore-runner of crystal detectors. In physical chemistry the detection of molecular change in matter under electric stimulation led to a new theory of photographic action. The theory of stereo-chemistry found strong support by the production of two kinds of artificial molecules, which, like the two kinds of sugar, rotated the polarized electric wave either to the right or to the left. Again the 'fatigue' of my receivers led to the discovery of sensitiveness inherent in matter as shown by its electric response. It was next possible to study this response in its modification under changing environment, of which its exaltation under stimulants and its abolition under poisons are among the most astonishing outward manifestations. And as a single example of the many applications of this fruitful discovery, the characteristics of an artificial retina gave a clue to the unexpected discovery of "binocular alternation of vision" in man:—each eye thus supplements its fellow by turns, instead of acting as a continuously yoked pair, as hitherto believed.
PLANT LIFE AND ANIMAL LIFE.
In natural sequence to the investigation of the response in "inorganic" matter, has followed a prolonged study of the activities of plant life as compared with the corresponding functioning of animal life. But since plants for the most part seem motionless and passive, and are indeed limited in their range of movement, special apparatus of extreme delicacy had to be invented, which should magnify the tremor of excitation and also measure the perception period of a plant to a thousandth part of a second. Ultra-microscopic movements were measured and recorded, the length measured being often smaller
