Introductory material

LECTURE I

Delivered on February 1st

Gentlemen,—Colour-blindness is not a good name for the condition to which it is applied, and still worse is the use of the term red-blindness or green-blindness. In the majority of cases of colour-blindness there is no blindness to colours in the ordinary acceptation of the term; a green, red, or yellow light produces a very definite sensation of colour. Those who confuse red and green do so, not because they see red as green or green as red, but because both give rise to a similar sensation of colour. The word light must be used in the sense of referring to those waves which excite the organ of vision. Because two stimuli excite a sensation of light, it does not follow that they are similar. We cannot, for instance, distinguish by the eye polarised light from non-polarised light. We have to distinguish between the physical stimuli by their physical properties apart from their effect on the organ of vision. I propose to divide the subject into two parts, and in this lecture to deal with the theory and facts of colour-vision and colour-blindness, and in the second lecture with the detection of colour-blindness from a practical point of view.