Lecture I

THE THEORY AND FACTS OF COLOUR-VISION AND COLOUR-BLINDNESS

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THE VISUAL PURPLE THE ESSENTIAL FACTOR IN VISION 11

1. Anatomical Evidence 11

2. Physiological Analogy with other Body Cells 12

3. The Relation between the Foveal and the Extra-Foveal Regions 13

4. The varying Sensibility of the Fovea 13

5. Chemical Analogy 14

6. Disappearance of Lights falling upon Fovea 15

7. Illusion of Moving Light 16

8. Purple After-Image 17

9. Currents seen in the Field of Vision not due to the Circulation 17

10. Pressure Figure 19

11. Macular Star 19

12. Entoptic Appearance of Cone Mosaic 20

13. Visual Acuity 21

THE EVOLUTION OF THE COLOUR-SENSE 26

THE FACTS OF COLOUR-BLINDNESS 34

1. Defects of Light-Perception 35

2. Defects of Colour-Perception 38

THE TWO MAIN VARIETIES OF COLOUR-BLINDNESS:

1. Dichromic Vision 40

2. Trichromic Vision 42